Virtual environment construction apparatus, method, and computer readable medium

ABSTRACT

Preliminary experience of a match at a player&#39;s perspective is enabled. A virtual environment material storage  13  has stored therein virtual environment materials for reproducing a dynamic object and a static object on a virtual environment. A dynamic object sensing unit  11  chronologically measures a position and a posture of the dynamic object in a real environment and generates position and posture information composed of one movement action. A presentation sequence acquisition unit  17  obtains a presentation sequence including position and posture information of a plurality of different kinds of dynamic objects. A virtual environment construction unit  14  synthesizes a virtual environment material of the dynamic object and a virtual environment material of the static object based on the presentation sequence to construct the virtual environment.

TECHNICAL FIELD

The present invention relates to a virtual environment constructiontechnique for synthesizing a video taken from a virtual and movableviewpoint based on a video capturing a real environment.

BACKGROUND ART

In a sport match, one sometimes cannot fully exert his or her abilitywhen encountering a first situation he or she has not experiencedpreviously. In baseball, for example, a situation where a player hastrouble in handling a pitcher he or she meets for the first time can bedescribed by the expression “weak to a first-time opponent”. To addresssuch a situation, it would be effective for the player to experiencesome pitches of the pitcher from the player's perspective beforehand inthe same environment as an actual match.

It is however difficult in terms of feasibility to actually experiencethe next opponent's pitches beforehand. A common alternative to this isviewing a video of past pitches of the opponent captured from a stand orthe like; however, such a video is different from what the player seeswhen actually standing in a batter's box in terms of viewpoint and/orfield of view, thus is not adequate as preliminary experience of a matchsituation.

Non-patent Literature 1 describes a method for realizing preliminaryexperience from a player's perspective. In the method, a camera capableof capturing a 360° panoramic image (hereinafter, referred to as anomnidirectional camera) is installed at the position of the player'sperspective, and the player views a video from the player's perspectivecaptured by the omnidirectional camera on a head mounted display.

PRIOR ART LITERATURE Non-Patent Literature

-   Non-patent Literature 1: Ochi, D., Kunita, Y, Kameda, A., Kojima,    A., Iwaki, S., “Live streaming system for omnidirectional video”,    Virtual Reality (VR), 2015 IEEE, pp. 349-350, March 2015.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, the method described in Non-patent Literature 1 is difficult toimplement in terms of feasibility because it requires installation of acamera in a batter's box during a match. A further problem is that theplayer can only preliminarily experience a viewpoint at which the camerais installed when viewing a video thus captured by the camera.

In view of these situations, an object of the present invention is toprovide a technique for virtually constructing a match environment toenable one to experience a match from a player's perspective beforehand.

Means to Solve the Problems

To accomplish the object, a virtual environment construction apparatusof this invention is a virtual environment construction apparatus thatconstructs a virtual environment for viewing by a user based on a realenvironment in which a dynamic object and a static object are present,the virtual environment construction apparatus including: a virtualenvironment material storage that stores virtual environment materialsfor reproducing the dynamic object and the static object on the virtualenvironment; a dynamic object sensing unit that chronologically measuresa position and a posture of the dynamic object in the real environmentand generates position and posture information composed of one movementaction; a presentation sequence acquisition unit that obtains apresentation sequence including position and posture information of aplurality of different kinds of dynamic objects; and a virtualenvironment construction unit that synthesizes a virtual environmentmaterial of the dynamic object and a virtual environment material of thestatic object based on the presentation sequence to construct thevirtual environment.

Effects of the Invention

The virtual environment construction technique of the present inventionenables preliminary experience of a match from a player's perspective byvirtually constructing a match environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a functional configuration of a virtualenvironment construction apparatus in a first embodiment.

FIG. 2 is a diagram illustrating a data structure of a position/postureinformation table.

FIG. 3 is a diagram illustrating a data structure of a constituentmaterial incorporation list.

FIG. 4 is a diagram illustrating a functional configuration of a virtualenvironment construction apparatus in a second embodiment.

FIG. 5 is a diagram illustrating a functional configuration of a virtualenvironment construction apparatus in a third embodiment.

FIG. 6 is a diagram illustrating a data structure of a presentationsequence table.

FIG. 7 is a diagram showing a specific example of the presentationsequence table.

FIG. 8 is a diagram illustrating a processing procedure of a virtualenvironment construction unit.

FIG. 9 is a diagram showing a specific example of an application effecttable.

FIG. 10 is a diagram showing a specific example of pitch course.

FIG. 11 is a diagram illustrating a functional configuration of avirtual environment construction apparatus in a fourth embodiment.

FIG. 12 is a diagram illustrating a functional configuration of avirtual environment construction apparatus in a fifth embodiment.

FIG. 13 is a diagram illustrating a processing procedure of a virtualenvironment construction method in the fifth embodiment.

FIG. 14 is a diagram for describing an action database.

FIG. 15 is a diagram for describing an exemplary classification ofcourses.

FIG. 16 is a diagram for describing an exemplary classification ofcourses.

FIG. 17 is a diagram for describing classification of pitch types.

FIG. 18 is a diagram for describing how a sequence is generated.

FIG. 19 is a diagram for describing a modification of probabilitydistribution.

FIG. 20 is a diagram illustrating a functional configuration of a videopresentation apparatus in a sixth embodiment.

FIG. 21 is a diagram illustrating a processing procedure of a videopresentation method in the sixth embodiment.

FIG. 22 is a diagram showing a specific example of user state.

FIG. 23 is a diagram showing a specific example of user state.

FIG. 24 is a diagram showing a specific example of user state.

FIG. 25 is a block diagram showing a configuration of a virtualenvironment construction apparatus in a seventh embodiment.

FIG. 26 is a flowchart showing the operation of the virtual environmentconstruction apparatus in the seventh embodiment.

FIG. 27 is a diagram illustrating a virtual material position/postureinformation table.

FIG. 28 is a flowchart showing an example of the operation of a virtualspecial dynamic material generation unit.

FIG. 29 is a flowchart showing an example of the operation of asynchronization unit.

FIG. 30 is a schematic diagram showing an example of camera angle forreproducing the perspective of a batter standing in a batter's box.

FIG. 31 is a block diagram showing a configuration of a virtualenvironment construction apparatus in an eighth embodiment.

FIG. 32 is a flowchart showing the operation of the virtual environmentconstruction apparatus in the eighth embodiment during a preliminarypreparation phase.

FIG. 33 is a diagram illustrating a video information table.

FIG. 34 is a flowchart showing the operation of the virtual environmentconstruction apparatus in the eighth embodiment during a virtualenvironment generation phase.

FIG. 35 is a diagram illustrating a virtual material position/postureinformation table.

FIG. 36 is a flowchart showing an example of the operation of a similarvideo retrieval unit.

FIG. 37 is a flowchart showing an example of the operation of a virtualspecial dynamic material generation unit.

FIG. 38 is a flowchart showing an example of the operation of thesynchronization unit.

FIG. 39 is a diagram illustrating a functional configuration of avirtual environment construction apparatus in a ninth embodiment.

FIG. 40 is a diagram for describing a specific example for baseball.

FIG. 41 is a diagram illustrating a processing procedure of a dynamicobject construction unit.

FIG. 42 is a diagram for describing a discrepancy between an angle ofobservation and an angle of viewing.

FIG. 43 is a diagram for describing a specific example for tennis.

FIG. 44 is a diagram for describing a specific example for tennis.

FIG. 45 is a diagram showing an example of an original image or videoand mask information.

FIG. 46 is a diagram illustrating a functional configuration of a videopresentation apparatus in a tenth embodiment.

FIG. 47 is a diagram illustrating a processing procedure of a videopresentation method in the tenth embodiment.

FIG. 48 is a diagram showing experimental results.

FIG. 49 is a diagram showing a system configuration of an imageprocessing system.

FIG. 50 is a diagram showing a specific example of a synthesisinformation table.

FIG. 51 is a diagram showing a specific example of an optimal depthinformation table.

FIG. 52 is a diagram showing a specific example of contrast computationresults.

FIG. 53 is a diagram illustrating a processing procedure of an imageprocessing device in an eleventh embodiment.

FIG. 54 is a diagram illustrating a functional configuration of an imageprocessing device in a twelfth embodiment.

FIG. 55 is a diagram illustrating a processing procedure of the imageprocessing device in the twelfth embodiment.

FIG. 56 is a diagram illustrating a functional configuration of an imageprocessing device in a thirteenth embodiment.

FIG. 57 is a diagram for describing specific processing by a decisionunit in the thirteenth embodiment.

FIG. 58 is a diagram illustrating a processing procedure of the imageprocessing device in the thirteenth embodiment.

FIG. 59 is a diagram illustrating a functional configuration of an imageprocessing device in a fourteenth embodiment.

FIG. 60 is a diagram illustrating a processing procedure of the imageprocessing device in the fourteenth embodiment.

FIG. 61 is a diagram showing a system for obtaining a virtualomnidirectional image in a conventional system.

FIG. 62 is a diagram for describing a flow of image processing in animage processing system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will now be described in detail. Inthe drawings, components having the same functions are denoted with thesame numerals and repeated descriptions are omitted.

First Embodiment

First, a virtual environment construction apparatus according to a firstembodiment will be generally described. To start with, a dynamic objectsensing unit determines the position and posture of a dynamic objectwhich is to be preliminarily experienced (for example, the path of abaseball pitch or a tennis serve) at each time and stores the positionand posture information. It is assumed that position and postureinformation relating to a static object, which does not temporallychange, (for example, a stadium or a ground) is prestored. Hereinafter,an object for constituting a virtual environment, such as a ball and astadium, will be referred to as constituent material. Also, computergraphics (CG) data for reproducing a constituent material in a virtualenvironment will be referred to as virtual environment material, whichis also assumed to be prestored. Among constituent materials, a materialwhose position transitions with time and that makes movements isreferred to as dynamic material, a constituent material whose positiondoes not transition with time and that does not make movements isreferred to as static material, and a constituent material whoseposition is considered to not transition but that makes movements whilestaying at the position is referred to as special dynamic material. Inthe case of baseball, for example, a dynamic material will be abaseball, a static material will be a stadium, and a special dynamicmaterial will be a pitcher. Dynamic objects are formed from dynamicmaterials and special dynamic materials. A static object is a staticmaterial. Virtual environment materials relating to a static object isnot limited to CG data, but may be moving image or still image dataclipped from an actually captured video. A virtual environmentconstruction unit constructs a virtual environment by arranging virtualenvironment materials based on the position and posture information ofthe individual constituent materials. Finally, a drawing unit outputsthe virtual environment as a video such as an omnidirectional video.

The virtual environment construction apparatus in the first embodimentincludes a dynamic object sensing unit 11, a constituent materialposition/posture storage 12, a virtual environment material storage 13,a virtual environment construction unit 14, and a drawing unit 15, asshown in FIG. 1. By the virtual environment construction apparatusperforming the processes at steps described below, a virtual environmentconstruction method in the first embodiment is implemented.

The virtual environment construction apparatus is a special deviceconfigured by loading of a special program into a known or dedicatedcomputer having a central processing unit (CPU), main memory (randomaccess memory or RAM), and the like, for example. The virtualenvironment construction apparatus executes various kinds of processingunder control of the central processing unit, for example. Data input tothe virtual environment construction apparatus and/or data resultingfrom various kinds of processing are stored in the main memory, forexample, and data stored in the main memory is read as required to beutilized for other processing. Also, at least part of the processingcomponents of the virtual environment construction apparatus may beformed of hardware such as an integrated circuit. The storages providedin the virtual environment construction apparatus may be formed of mainmemory such as random access memory (RAM), an auxiliary storage deviceformed of a hard disk, optical disk, or a semiconductor memory devicesuch as a flash memory, or middleware such as a relational database or akey value store, for example. The storages provided in the virtualenvironment construction apparatus may be each logically partitioned orthey may be stored in a single physical storage device.

The dynamic object sensing unit 11 measures the position and posture ofa dynamic object in a real environment to generate position and postureinformation composed of one movement action. The generated position andposture information of the dynamic object is stored in the constituentmaterial position/posture storage 12. Specifically, a sensor (not shown)connected with the virtual environment construction apparatus measuresthe position and posture of a dynamic object during one movement action,and uses the resulting values as input to estimate three-dimensionalposition and posture information of the dynamic object. A dynamic objectrefers to an object whose three-dimensional position changes with timein a virtual environment, for example, a baseball or an opponent playersuch as a pitcher in the case of baseball, or a tennis ball or anopponent player such as a server in the case of tennis. One movementaction is an action corresponding to a single pitch by a pitcher in thecase of a baseball or an action corresponding to a single serve in thecase of a tennis ball, for example.

Multiple cameras may be utilized as sensors for computing thethree-dimensional position and posture of a dynamic object. A specificexample of an approach to compute three-dimensional position informationof a ball utilizing multiple cameras is one that employs triangulation.Specifically, for videos captured by cameras which have undergone cameracalibration in advance, the position of a ball on the images isdetermined. Here, the position of the ball on an image may be manuallygiven, or the ball may be detected via a detection approach such astemplate matching, and the center position thereof may be set as theposition of the ball. By applying triangulation using the positionsdetected in the images and camera parameters determined in cameracalibration, the three-dimensional position of the ball can bedetermined. For the posture, to how much extent the ball is rotatedrelative to a reference posture can be determined, for example, from astitching pattern on the ball captured in an image. Other examples ofsensors for determining the position and posture of a dynamic objectinclude a Doppler radar. As this sensor is a well-known technique,detailed description of the sensor is omitted. Any other sensors andapproaches that are capable of obtaining three-dimensional position andposture information of a ball may be used.

The constituent material position/posture storage 12 stores position andposture information relating to constituent materials. Position andposture information relating to a dynamic object is generated and storedby the dynamic object sensing unit 11. Position and posture informationrelating to a static object is prepared and stored in advance.Specifically, a constituent material position/posture information tablecomposed of records each representing three-dimensional position andposture information of each constituent material at each time is stored.

The constituent material position/posture information table includes a“constituent material ID” uniquely identifying a constituent material, a“virtual environment material ID” uniquely identifying a virtualenvironment material, and “position” and “posture” values of an objectat each “time” as shown in FIG. 2. Position is represented as athree-dimensional translation vector, and posture is represented as athree-dimensional vector that represents a rotation angle relative toeach axis. For example, when assuming baseball pitching and imaginingthat constituent material Oi represents a straight ball, virtualenvironment material Ei corresponding to the constituent material Oiwould be CG data for a baseball stored in the virtual environmentmaterial storage 13. Then, the position and posture corresponding toeach time represents at which position and in which posture the ball ispresent at that time. More specifically, positions Ti(0), Ti(1), . . . ,Ti(ti) represent the ball path, and postures Ri(0), Ri(1), . . . ,Ri(ti) represent how the ball is rotating. In FIG. 2, a constituentmaterial with “-” stored in the time means that it is a static object,which does not change in position or posture with time, such as astadium. It is assumed that position and posture information of such astatic object is prestored. Also, a time defined for a constituentmaterial represents the time elapsed since when the constituent materialwas incorporated into a virtual environment by the virtual environmentconstruction unit 14, which is discussed later. Specifically, if theconstituent material Oi is incorporated into the virtual environment atthe point of time ta, the position and posture of the constituentmaterial Oi at time (ta+0) are Ti(0) and Ri(0) respectively, and theposition and posture of the constituent material Oi at time (ta+1) areTi(1) and Ri(1) respectively.

The virtual environment material storage 13 stores a virtual environmentmaterial corresponding to each constituent material. A virtualenvironment material is a material for constructing a virtualenvironment, such as CG data or live-action data, for example. Thevirtual environment material storage 13 stores each virtual environmentmaterial in association with a virtual environment material ID. Examplesof virtual environment material are CG data for a stadium or a baseballin the case of baseball, or CG data for a tennis court or a tennis ballin the case of tennis. It is assumed that they are prepared and storedbeforehand.

The virtual environment construction unit 14 reads position and postureinformation of each constituent material from the constituent materialposition/posture storage 12, reads data for the virtual environmentmaterial corresponding to the constituent material from the virtualenvironment material storage 13, and synthesizes a virtual environmentmaterial of a dynamic object with a virtual environment material of astatic object, thereby constructing virtual environment data. Theconstructed virtual environment data is sent to the drawing unit 15. Thevirtual environment data refers to a virtual space in which data for oneor more virtual environment materials have been arranged in a certainvirtual space. As a specific example, a procedure for creating virtualenvironment data in the case of baseball will be described. First, aconstituent material incorporation list for constructing a virtualenvironment is read. The constituent material incorporation listincludes a “constituent material ID” uniquely identifying a constituentmaterial and “time” indicating when the constituent material isincorporated into a virtual environment, as shown in FIG. 3. It isassumed that the constituent material incorporation list is manuallyprepared in advance. For example, in the case of creating virtualenvironment data for baseball, constituent material IDs and timesrelating to a stadium, a pitcher, a ball, and the like are described inthe constituent material incorporation list. Next, if there is aconstituent material to be drawn at each time, a virtual environmentmaterial corresponding to that constituent material is incorporated intothe virtual environment. Here, the position and posture of theconstituent material are read from the constituent materialposition/posture storage 12, and the constituent material is arranged inthe virtual space based on the position and posture. After all theconstituent materials described in the constituent materialincorporation list have been incorporated into the virtual environment,the processing is terminated.

The drawing unit 15 outputs the constructed virtual environment data ina format viewable by the user. The video being output may be a videothat sees one direction from a certain viewpoint in a virtualenvironment or a video that allows viewing in all directions like anomnidirectional video. For instance, in the case of outputting a videothat sees one direction from a certain viewpoint, a perspectiveprojection camera C may be virtually set at a certain position and a CGmodel present in the virtual environment space may be projected onto theimage plane of the camera C. Specifically, when T is a position as anextrinsic parameter of the camera C, R is the posture, and K is anintrinsic parameter, a certain point p within the space in which thevirtual environment data exists will be projected as point q on theimage plane of the camera C as follows.q=K(Rp+T)

Here, the intrinsic parameter K is a 3×3 matrix composed of the focaldistance and/or the image center of the camera C.

In the case of outputting an omnidirectional video that allows viewingin all the directions from a certain viewpoint, an omnidirectionalcamera O may be virtually set at the certain viewpoint and a CG modelpresent in the virtual environment space may be projected onto the imageplane of the camera O. Specifically, when T is a position as anextrinsic parameter of the camera O, R is the posture, W is the width ofthe image plane of projection, and H is the height thereof, a certainpoint p within the space in which the virtual environment data existswill be projected as point q=(q_(x), q_(y))^(T) onto the image plane ofthe camera O as follows.

p^(′) = Rp + T = (p_(x)^(′)p_(y)^(′)p_(z)^(′))^(T)$q_{x} = {( \frac{\theta\; W}{2\pi} ) + \frac{W}{2}}$$q_{y} = \frac{\varphi\; H}{\pi}$where

${\theta = {\arctan( \frac{p_{z}^{\prime}}{p_{x}^{\prime}} )}},{\varphi = {\arccos( \frac{p_{y}^{\prime}}{p^{\prime}} )}}$

While the present example employs equidistant cylindrical projection asa projection for representing an omnidirectional video as atwo-dimensional image, other kinds of projection such as Mercator'sprojection may be employed.

Second Embodiment

In the first embodiment, the drawing unit outputs only a video from apredefined viewpoint in a virtual environment. Thus, experience such asfreely moving in a virtual environment is difficult to implement.Although output of videos at all points would possible, it is notrealistic in terms of throughput. The second embodiment adds a usersensing unit for sensing the position and posture of a user to theconfiguration of the first embodiment and senses a position and adirection in which the user wants to view, thereby allowing the user toview a video while freely moving in a virtual environment.

The virtual environment construction apparatus in the second embodimentincludes the dynamic object sensing unit 11, the constituent materialposition/posture storage 12, the virtual environment material storage13, the virtual environment construction unit 14, and the drawing unit15 similarly to the first embodiment, and further includes a usersensing unit 16, as shown in FIG. 4. By the virtual environmentconstruction apparatus performing the processes at steps describedbelow, a virtual environment construction method in the secondembodiment is implemented.

In the following, a processing procedure of the virtual environmentconstruction method in the second embodiment will be described mainlyfor differences from the first embodiment.

The user sensing unit 16 measures the position and posture of the headof the user to generate user position and posture information. Thegenerated user position and posture information is sent to the drawingunit 15. Specifically, a sensor (not shown) provided in the virtualenvironment construction apparatus measures the position and posture ofthe user's head, and uses the resulting values as input to estimatethree-dimensional position and posture information of the user's head.

The sensor for computing the three-dimensional position and posture ofthe user's head may be any kind of sensor. A specific example of such asensor is a motion sensor represented by those from OptiTrack.Alternatively, a head mounted display (HMD) represented by those fromOculus and an accompanying infrared (IR) camera may be employed. As theyare implemented using well-known techniques, detailed descriptions ofthese are omitted.

The drawing unit 15 outputs virtual environment data in a formatviewable by the user based on the user position and posture informationreceived from the user sensing unit 16. Here, it may output a video inthe direction of the user's line of sight in a virtual environment ormay output an omnidirectional video.

Third Embodiment

In general, contents of training vary depending on what kind of abilityone wants to improve. For example, when one wants to physically learnthe feeling of tennis serves, intensive practice of serving would beeffective. When one aims at increasing the strength of a serve,correction of his or her usage of the body or muscle training would beeffective. The third embodiment enables change to a virtual environmentthat will be constructed depending on the user's practice goal by addinga presentation sequence acquisition unit to the first embodiment.

The virtual environment construction apparatus in the third embodimentincludes the dynamic object sensing unit 11, the constituent materialposition/posture storage 12, the virtual environment material storage13, the virtual environment construction unit 14, and the drawing unit15 similarly to the first embodiment, and further includes apresentation sequence acquisition unit 17, as shown in FIG. 5. By thevirtual environment construction apparatus performing the processes atsteps described below, a virtual environment construction method in thethird embodiment is implemented.

In the following, a processing procedure of the virtual environmentconstruction method in the third embodiment will be described mainly fordifferences from the first embodiment.

The presentation sequence acquisition unit 17 obtains a presentationsequence stored in the constituent material position/posture storage 12and representing a scene to be viewed by the user, including positionand posture information of multiple kinds of different dynamic objects.The obtained presentation sequence is sent to the virtual environmentconstruction unit 14. Specifically, input from the user is obtained, anda record relating to the presentation sequence corresponding to theuser's input is extracted and output from a prepared presentationsequence table. Input from the user may be obtained in any manner, suchas entering a key from a keyboard, clicking with a mouse, or entering akey using a game controller, for example. The presentation sequencetable is composed of “practice goal”, “constituent material ID”corresponding to the practice goal, and “time” at which each constituentmaterial is incorporated into a virtual environment, as shown in FIG. 6.For example, in the example of FIG. 6, for the practice goal “want toimprove the ◯◯ ability”, constituent material O1 is incorporated at timet1 and the constituent materials O2 and O3 are incorporated at time t2.Note that the time here is the time elapsed since the point of output tothe virtual environment construction unit 14. That is, if a record(presentation sequence) relating to the practice goal “want to improvethe ◯◯ ability” is output at a certain time t, constituent material O1will be incorporated into a virtual environment at time (t+t1) and theconstituent materials O2 and O3 will be incorporated into a virtualenvironment at time (t+t2). It is also assumed that in the presentationsequence table, each presentation sequence corresponds to a certain userinput and such correspondences are predefined. That is, when a certainkey is pressed, a record (a presentation sequence) relating to thepractice goal “want to improve the ◯◯ ability” will be output. FIG. 7 isa specific example of a presentation sequence table for baseball as anexample.

The virtual environment construction unit 14 takes data on virtualenvironment materials, position and posture information of eachconstituent material, and the presentation sequence table as input, andconstructs virtual environment data. FIG. 8 is a diagram illustratingthe processing procedure of the virtual environment construction unit 14in this embodiment. It is assumed that virtual environment constructionunit 14 maintains the constituent material incorporation list shown inFIG. 3 in advance.

At step S11, the virtual environment construction unit 14 determineswhether there has been input of the presentation sequence table at acertain time t or not. If there has been input (YES), the flow proceedsto step S12, and if there has been no input (NO), the flow proceeds tostep S13. At step S12, the presentation sequence table is merged withthe constituent material incorporation list. The merging of the table isperformed using time as key. If there has been input of the presentationsequence table shown in FIG. 6 at a certain time t, the constituentmaterial O1 is incorporated into the virtual environment at time (t+t1)and the constituent material O2 is incorporated into the virtualenvironment at time (t+t2). At step S13, it is determined whether thereis any constituent material that should be incorporated at time t ornot. If there is a constituent material that should be incorporated(YES), the flow proceeds to step S14, and if there is no constituentmaterial that should be incorporated (NO), the flow proceeds to stepS15. At step S14, the constituent material in question is incorporatedinto the virtual environment. At step S15, the virtual environmentcurrently being constructed is output to the drawing unit 15. Then, atstep S16, t is set to t=t+1 and the process returns to step S11.

In the following, taking a baseball batter as an example, an ability onewants to improve and the way of improving it will be described morespecifically. In this specific example, as shown in FIG. 9, attributessuch as “ball speed”, “course”, and “pitch type” are additionallymaintained for each pitch during creation of the presentation sequencetable, which is utilized in the presentation sequence acquisition unit17, for easy and intuitive understanding of what kind of pitches shouldbe performed in which sequence. These attributes can be determined fromchange in the position and posture of each constituent material storedin the constituent material position/posture storage 12. For example, aball speed can be determined by dividing a distance travelled within acertain time by that time. Course can be determined by segmenting aplane on a home base as shown in FIG. 10 and determining the regionclosest to a ball when the ball passes over the plane. Pitch type can bedetermined by using the velocity vectors of the ball immediately afterit is released and when it is received in a catcher's mitt (v1 and v2,respectively). For example, when v1 and v2 are in substantially the samedirection, it indicates a straight ball; when the direction of v2 isoriented vertically downward in comparison between v1 and v2, itindicates a forkball; and when v2 is oriented obliquely downward, itindicates a curveball. These attributes are maintained for constituentmaterials corresponding to pitches. These are examples of attributes forbaseball pitching and may be different attributes in the case of socceror tennis according to the characteristics of the sport in question.

(a) Improving the Ability for Variation in Speed

When a slow ball is pitched after a fast ball or a fast ball is pitchedafter a slow ball, one may fail to swing a bat at an appropriate timingdue to influence of the timing of the immediately preceding ball. Toaddress it, the ability for variation in speed would be improved byexperiencing fast balls and slow balls in a random order. In this case,the presentation sequence acquisition unit 17 prepares constituentmaterial IDs in advance so that random pitches will be provided,allowing the user to perform training for the ability for such variationin speed. Exemplary orders of pitches for such a training are shownbelow.

Exemplary order of pitches (i): a straight ball (ball speed 140 km/h)-acurveball (ball speed 120 km/h)-a straight ball (ball speed 150 km/h)-aslow ball (ball speed 110 km/h) . . . .

Exemplary order of pitches (ii): a straight ball (ball speed 140 km/h)-astraight ball (ball speed 145 km/h)-a curveball (ball speed 120 km/h)-astraight ball (ball speed 135 km/h)-a straight ball (ball speed 140km/h) . . . .

The pitches in these exemplary orders of pitches may take any course.The presentation sequence table for the exemplary order of pitches (i)is shown as the specific example in FIG. 7. Also, such an order ofpitches may be determined either manually or automatically. In the caseof automatic determination, pitch types may be randomly selected fromall pitch types, or a pitch with a ball speed higher than a predefinedthreshold th may be categorized into group 1 and a pitch with a ballspeed lower than the threshold th may be categorized into group 2, andpitch types may be randomly selected such that selection is made at apredefined ratio from the two groups (for example, ten from group 1 andfive from group 2), for example.

(b) Improving Batting Eye (the Ability to Distinguish a Strike from aBall)

Correct judgment is difficult with a ball that is pitched around theboundary between the strike zone and the ball zone. To address it, thebatting eye could be improved by repeatedly experiencing a pitch judgedas a strike and a pitch judged as a ball alternatingly in similar paths.Another example of a common order of pitches is once pitching to thebatter's chest and then outside low. This is believed to have the effectof retarding the batter's response or blurring judgment between a strikeand a ball by once accommodating the batter's eyes to around the chestand then pitching a ball outside low, that is, farthest from the chest.To address it, the batting eye would be improved by repeatedlyexperiencing a pitch to one corner of the strike zone and a pitch to thediagonally opposite corner alternatingly. By the presentation sequenceacquisition unit 17 preparing constituent material IDs so that pitcheswill be provided in such a manner, the user can perform training forimproving his or her batting eye.

Exemplary order of pitches (iii): a straight ball (course 2-A)-astraight ball (course 2-B)-a straight ball (course 1-B)-a straight ball(course 2-B) . . . .

Exemplary order of pitches (iv): a straight ball (course 4-D)-a straightball (course 2-B)-a straight ball (course 4-D)-a straight ball (course2-D) . . . .

The pitches in these exemplary orders of pitches may be delivered at anyball speed. The presentation sequence table for the exemplary order ofpitches (iii) is shown as the specific example in FIG. 7.

While the virtual environment construction apparatus in the thirdembodiment has been described for configuration and processing procedureon the basis of the configuration of the first embodiment, it may beconfigured on the basis of the configuration of the second embodiment.That is, the virtual environment construction apparatus in the thirdembodiment may further include the user sensing unit 16.

Fourth Embodiment

The first to third embodiments assume that training is performed withconstruction of a trajectory that has been actually obtained, that is,the same environment as reality. However, some training methodologiesare intended to improve the performance in an actual match byexperiencing a more demanding environment than the reality. In baseball,for example, a player may experience pitches from a position closer thanan actual mound in order to accommodate his or her eyes to fast balls,or may perform practice swing in an on-deck circle using a training batheavier than a usual bat. The fourth embodiment realizes a virtualenvironment for experiencing a more demanding environment than thereality by additionally including an effect application unit.

The virtual environment construction apparatus in the fourth embodimentincludes the dynamic object sensing unit 11, the constituent materialposition/posture storage 12, the virtual environment material storage13, the virtual environment construction unit 14, the drawing unit 15,and the presentation sequence acquisition unit 17 similarly to the thirdembodiment, and further includes an effect application unit 18, as shownin FIG. 11. By the virtual environment construction apparatus performingthe processes at steps described below, a virtual environmentconstruction method in the fourth embodiment is implemented.

In the following, a processing procedure of the virtual environmentconstruction method in the fourth embodiment will be described mainlyfor differences from the third embodiment.

The presentation sequence acquisition unit 17 in this embodiment outputsinformation on an application effect in addition to a presentationsequence. The information on the application effect is sent to theeffect application unit 18 along with the presentation sequence. Anapplication effect refers to the function of an effect to be applied toa constituent material corresponding to a constituent material ID. Forexample, it may be an effect for increasing visual load on the user.Specifically, such an effect may be changing the rate of change in theposition and posture of a constituent material (for example, increasingor decreasing of the ball speed, or increasing the amount of rotation),or providing a special effect relating to the appearance of aconstituent material, such as making it transparent in midstream. It isassumed that an application effect corresponding to a certain user inputis predefined, such as the ball speed being increased when a certainbutton is clicked.

The effect application unit 18 takes data on a virtual environmentmaterial, position and posture information of each constituent material,and information on an application effect as input, and outputs the dataon the virtual environment material and the position and postureinformation of each constituent material on which an effect has beenapplied based on the information on the application effect.

In the following, how an effect is applied will be described morespecifically taking baseball as an example like the third embodiment.

(a) Improving the Batting Ability for a Fast Ball

When one is visually and/or physically accustomed to fast balls, he orshe would be able to swing a bat for a slower ball at an appropriatetiming with leeway. However, when the trajectories of balls actuallythrown by a pitcher are acquired, it is not always the case that thepitcher is able to pitch faster balls than any pitcher. In such a case,the presentation sequence acquisition unit 17 issues an instruction foran application effect “increase the ball speed by 10 km/h”. Assumingthat the ball speed of pitch Oi input to the effect application unit 18is v1 in this case, the position and posture of a pitch with a ballspeed increased by 10 km/h can be determined by multiplying the amountof change of the position and posture of Oi per unit time by((v1+10)/v1). Using it, training for improving the batting ability forfast balls can be performed.

(b) Improving the Batting Ability for Breaking Balls

When one is visually and/or physically accustomed to breaking balls witha large amount of change, he or she would be able to swing a bat atappropriate timing and position with leeway for a ball with a smallamount of change. However, when the position and posture of ballsactually thrown by a pitcher are acquired, it is not always the casethat the pitcher is able to pitch breaking ball with an appropriateamount of change. In such a case, the presentation sequence acquisitionunit 17 issues an instruction for an application effect “increase theamount of change of the ball by Δa %”. If the acceleration of pitch Oiinput to the effect application unit 18 is a at a certain point in thiscase, position and posture of a breaking ball with a greater amount ofchange can be created by re-calculating the position and posture withaddition of Δa to the acceleration. With this, training for improvingthe batting ability for breaking balls can be performed.

(c) Improving the Ability to Grasp an Overall Path from an Early Path ofa Pitch

For a ball speed of 130 km/h, there is only about 0.5 seconds from whenthe ball is released to when it is received by the catcher's mitt,leading a problem of delayed timing of swinging a bat after the batterdelays the determination of the course or pitch type until the lastminute. In such a case, the presentation sequence acquisition unit 17issues an instruction for an application effect “obscure the ball”. Theeffect application unit 18 then incorporates CG of a normal baseball upto a point d meters away from the point of release in relation to apitch given as input, and applies an effect to obscure the ball afterthe d-meter point (for example, making it transparent or graduallymaking it transparent). The value of d and/or the effect to be appliedmay be set as appropriate. By the presentation sequence acquisition unit17 alternatingly incorporating a pitch with such an obscuring effectapplied and an identical pitch without application of the effect, theuser can perform training for predicting the overall path of a pitchfrom an early path of the pitch, that is, change in the position andposture of the ball from the point of release to the point d meters awayfrom it.

While the virtual environment construction apparatus in the fourthembodiment has been described for configuration and processing procedureon the basis of the configuration of the first embodiment, it may beconfigured on the basis of the configuration of the second embodiment.That is, the virtual environment construction apparatus in the fourthembodiment may further include the user sensing unit 16.

Fifth Embodiment

For training of sports and the like, for example, systems have beenproposed that aim at improving performance in a match by virtuallyproducing an experience close to a match and allowing a player toexperience it beforehand (Reference Literature 1, for instance).Reference Literature 1 describes a system for coaching a footballplayer, in which a 360° video from the player's perspective thatreproduces the same environment as a match using virtual reality (VR)technique is viewed on a head mounted display.

-   Reference Literature 1: STRIVR Labs, Inc., “STRIVR| Immersive    Training Solutions”, [online], [searched on Jan. 4, 2017], the    Internet <URL: http://www.strivrlabs.com/home/about-us>

In sports practice, one often experiences a more demanding environmentthan an actual match for the purpose of improving his or her performancein a match. For example, a female team may practice with a male team asan opponent, or a baseball batter may experience faster balls by apitcher throwing at a position closer than the mound, or a batter mayswing a bat heavier than one used in a match. However, the conventionaltechnique described in Reference Literature 1 just presents a realsituation captured in advance as it is and does not enable experience ofa more demanding environment than the reality.

In view of the foregoing, an object of the fifth embodiment is toprovide a virtual environment construction technique that enablesexperience of a virtual environment more demanding than the realitybased on information obtained from a real environment.

To accomplish the object, a virtual environment construction apparatusaccording to a first aspect of the fifth embodiment is a virtualenvironment construction apparatus that constructs a virtual environmentto be experienced by a user based on a real environment in which anotherparty launches a flying object, the virtual environment constructionapparatus including: a presentation sequence generation unit thatgenerates a presentation sequence representing a time series of scenesto be presented to the user based on a probability combining a priorprobability of a scene of the flying object with dynamics representingconnection between a plurality of scenes; a presentation trajectorydecision unit that decides a presentation trajectory representing amotion of the flying object corresponding to each scene included in thepresentation sequence; a presentation action decision unit that decidesa presentation action representing a motion of the other partycorresponding to each scene included in the presentation sequence; andan experience synthesis unit that synthesizes the virtual environment tobe experienced by the user based on the presentation trajectory and thepresentation action.

The virtual environment construction apparatus according to a secondaspect of the fifth embodiment is a virtual environment constructionapparatus that constructs a virtual environment to be experienced by auser based on a real environment in which another party launches aflying object, the virtual environment construction apparatus including:a presentation sequence generation unit that generates a presentationsequence representing a time series of scenes to be presented to theuser; a presentation trajectory decision unit that decides apresentation trajectory representing a motion of the flying objectcorresponding to each scene included in the presentation sequence; apresentation action decision unit that decides a presentation actionrepresenting a motion of the other party different from one in the realenvironment corresponding to each scene included in the presentationsequence; and an experience synthesis unit that synthesizes the virtualenvironment to be experienced by the user based on the presentationtrajectory and the presentation action.

The fifth embodiment aims at improving sports performance throughvirtual experience. Here, assume a situation where an action of anotherparty and associated movement of a ball occur in a certain phase of asport, and one is trained for an action to handle it. For example,assume a situation such as a baseball batter hitting a ball thrown by apitcher, a soccer keeper catching a ball kicked by a kicker in a penaltykick, a tennis receiver hitting back a ball hit by a server, or avolleyball receiver receiving a ball hit by a server. Hereinafter, aperson that launches a ball, such as a pitcher, kicker, and server aslisted above, will be referred to as “opponent player” or just “anotherparty”. Also, a video equivalent to a single pitch will be referred toas “scene” and a succession of multiple scenes will be referred to as“sequence”. Also, information on ball motion will be referred to as“trajectory” and information on motion of an opponent player will bereferred to as “action”. The “trajectory” and the “action” may be avideo captured in a real environment, or may be chronologicalarrangement of three-dimensional position information of an object orperson as a subject.

Sports to which the fifth embodiment is applicable are not limited tosports that use a ball, such as those mentioned above. It may beutilized in sports and situations in general where some object islaunched from an opponent player, such as Frisbee, for example.Hereinafter, an object that is launched by an opponent player, includinga ball as described above, will be referred to as “flying object”.

The virtual environment construction apparatus in the fifth embodimentincludes a trajectory storage 21, an action storage 22, a practice goalacquisition unit 23, a presentation sequence generation unit 24, apresentation trajectory decision unit 25, a presentation action decisionunit 26, an experience synthesis unit 27, and an experience presentationunit 28, as shown in FIG. 12. By the virtual environment constructionapparatus performing the processes at steps shown in FIG. 13, a virtualenvironment construction method in the fifth embodiment is implemented.

The virtual environment construction apparatus is a special deviceconfigured by loading of a special program into a known or dedicatedcomputer having a central processing unit (CPU), main memory (randomaccess memory or RAM), and the like, for example. The virtualenvironment construction apparatus executes various kinds of processingunder control of the central processing unit, for example. Data input tothe virtual environment construction apparatus and/or data resultingfrom various kinds of processing are stored in the main memory, forexample, and data stored in the main memory is read as required to beutilized for other processing. Also, at least part of the processingcomponents of the virtual environment construction apparatus may beformed of hardware such as an integrated circuit. The storages providedin the virtual environment construction apparatus may be formed of mainmemory such as random access memory (RAM), an auxiliary storage deviceformed of a hard disk, optical disk, or a semiconductor memory devicesuch as a flash memory, or middleware such as a relational database or akey value store, for example. The storages provided in the virtualenvironment construction apparatus may be each logically partitioned orthey may be stored in a single physical storage device.

Referring to FIG. 13, the processing procedure of the virtualenvironment construction method in the fifth embodiment is described.

The trajectory storage 21 has stored therein a trajectory databaseaccumulating trajectory data in which action IDs, opponent player IDs,and trajectory information are associated with one another. An action IDis an identifier uniquely identifying an action of an opponent player.An opponent player ID is an identifier uniquely identifying an opponentplayer. Trajectory information is information representing thetrajectory of a flying object after an action of the opponent player,assumed here to be a chronological arrangement of three-dimensionalposition information of the flying object.

The action storage 22 has stored therein an action database accumulatingaction data in which action IDs, opponent player IDs, and action videosare associated with one another. Action video may maintainthree-dimensional action information including depth, or may betwo-dimensional (that is, a normal video).

FIG. 14 shows an example of the action database. In the action database,action videos are stored by setting frame images 1 to T corresponding totimes 1 to T for an action ID and an opponent player ID (see action ID=1and opponent player ID=1 in FIG. 14). Also, information that enablesdynamic generation of action video may be set, such as three-dimensionalcoordinates of a body part (such as a hand or arm) of an opponentplayer, at times 1 to T for an action ID and an opponent player ID (seeaction ID=2 and opponent player ID=1 in FIG. 14).

It is assumed that trajectory data stored in the trajectory database andaction data stored in the action database are associated with each otheron a one-to-one basis and cross reference between them is possible. Thatis, a combination of an action ID and an opponent player ID uniquelydetermines action data and trajectory data.

At step S21, the practice goal acquisition unit 23 obtains informationincluding at least a practice goal of a practice goal and a practiceintensity from an input unit not illustrated, for example, a keyboard,and outputs it. Practice goal is information representing a scene to beexperienced by the user. Practice intensity is information representingthe difficulty level of practice. Practice goal and practice intensityare obtained by presenting multiple entries prepared in advance to theuser by displaying them on a display, for example, and prompting theuser to select one or more of the entries via touch panel operation,keyboard entry, or the like by the user. Practice goal and practiceintensity do not have to be selected on each use, and may be obtained byreading settings made by the user beforehand. In the subsequent process,a configuration that does not employ practice intensity is possible, inwhich case only the practice goal has to be obtained.

Practice goal is specifically selected from entries such as:

1. Course distinction enhancement,

2. Speed enhancement, and

3. Speed change enhancement, for example.

For the course distinction enhancement of 1, further options areprepared such as:

1-1. high/low,

1-2. outside strike/ball,

1-3. inside strike/ball,

1-4. targeted ball/others.

For the speed enhancement of 2, further options are prepared such as:

2-1. ◯◯ km/h to ΔΔ km/h

2-2. ΔΔ km/h to □□ km/h

. . .

For the speed change enhancement of 3, further options are prepared suchas:

3-1. Two types (straight ball and curveball),

3-2. Three types (straight ball, curveball, and slider),

3-3. Four types (straight ball, curveball, slider, and change-up)

. . .

The practice intensity is set as integers from 1 to 6, for example,which may be defined as:

1. Practice with a video of a real pitcher that delivered the pitch tobe trained;

2. Practice with a video in which a real pitcher is replaced with astick figure;

3. Practice with a video of one of multiple template pitchers prepared;

4. Practice with the same video of the same pitcher throughout;

5. Practice with a video modified so that the pitcher's hand is notvisible;

6. Practice with a video showing nothing at the location where thepitcher should be present.

While in the above example the difficulty level becomes higher as thevalue of the practice intensity increases, such definition is notnecessarily required.

If a practice intensity is input, the practice goal acquisition unit 23outputs the practice intensity to the experience synthesis unit 27.

At step S22, the presentation sequence generation unit 24 receives thepractice intensity from the practice goal acquisition unit 23, andgenerates and outputs a presentation sequence representing the timeseries of scenes to be presented to the user based on the practice goal.

In the presentation sequence, pieces of scene information, includinginformation on course, speed, and pitch type, for example, are arrangedas many as the number of scenes to be presented. Here, the number ofscenes refers to the number of pitches in baseball, for example, not thenumber of frames in a video. Scene information is set as follows, forexample.

Presentation No. 1: course=(1, 3), speed=140 km/h, pitch type=straightball

The course is two-dimensionally represented, including ball zonesfalling outside the strike zone on the top, bottom, left, and right, bydividing the strike zone into 3×3, or nine, blocks in the horizontal andvertical directions as shown in FIG. 15, where the horizontal directionis the x-axis and the vertical direction is the y-axis. FIG. 15 is anexample of course classification for a case where the lower left cornerof the strike zone seen from the batter's side, enclosed by a bold line,is defined as the origin. For example, course=(1, 3) indicates a ballthat passes through the block that is positioned first from the left andthird from the bottom among the nine blocks of the strike zone (aninside, higher strike zone seen from a right-handed batter). Fordesignation of a ball zone, values equal to or smaller than 0 or equalto or greater than 4 may be set. For example, course=(4, 0) indicates aball that passes through the block that is one block outside the strikezone to the right and one block outside to the bottom (an outside, lowerball zone seen from a right-handed batter). However, classification isnot limited thereto but may be made in a different way, such as5-classification, which divides a space including above the home baseand the strike zone into five positions: “top”, “middle left”, “middleright”, “lower left”, and “lower right” as shown in FIG. 16, forexample. For designation of ball zones, spaces falling outside thestrike zone on the top, bottom, left, and right may be divided into“upper outside (a space further above the ‘top’)”, “upper left outside(a space to the left of ‘top’)”, “upper right outside (a space to theright of ‘top’)”, “middle left outside (a space further left of the‘middle left’)”, “middle right outside (a space further right of the‘middle right’)”, “lower left outside (a space further left of the‘lower left’)”, “lower right outside (a space further right of the‘lower right’)”, and “lower outside (a space further below the ‘lowerleft’ and ‘lower right’)”, for example.

Pitch types may be classified in any manner. For example, a pitch typeclassification may be defined with a range of speed and a magnitude ofchange, as shown in FIG. 17. In the example of FIG. 17, pitch typeclassification is defined on a graph with speed indicated on thehorizontal axis and change on the vertical axis, where a shorterdistance on the graph represents closer pitch types. In general, pitchtypes are considered to be closer in the order of straight ball, slider,change-up, curveball, and forkball. Consideration of similarity of pitchtypes enables more flexible practice. For example, control becomespossible such that pitch types of high similarity will not be repeatedover a predetermined number of times, or such that pitches separate fromeach other in similarity by a predetermined value or more will beprovided in succession.

The classification can be considered to indicate the distance betweenones classified into the same class as 0, and otherwise as 1. Definingclassification as in FIG. 17 enables flexible control in terms ofdynamics, which is discussed later, because it allows the similaritybetween pitch types to be treated as a continuous distance.

Classification and/or similarity specific to individual opponent players(for example, pitchers in baseball, or servers in tennis) may also beprepared.

The presentation sequence generation unit 24 maintains prior probabilityp(s) and dynamics p(s_(t+1)|s_(t)) determined beforehand. Here, t is anumber representing an index of a scene, and s is a parameter relatingto the flying of a flying object in a certain scene, for example, one ofcourse, speed, and pitch type. The prior probability of each parametermay be determined by computing an average from a database in whichpitches of various types delivered by various pitchers are recorded, forexample. The dynamics of a parameter may be determined from transitionof the parameter in consecutive pitches delivered by a pitcher (changebetween the previous pitch to the next pitch), for example.

The method of creating a presentation sequence will be shown below.Since consecutive viewing of an identical scene can lower the effect ofpractice, an order of pitches that promotes effective practice isgenerated in a presentation sequence in accordance with the practicegoal. The presentation sequence generation unit 24 creates a prototypeof the presentation sequence. For example, a course is created in themanner as described below, and speed and pitch type are randomlydetermined and output.

As shown in FIG. 18, course (x₁, y₁) for the first pitch is decidedfirst by random sampling from the prior probability p(s). The course isdecided based on definition similar to the course classification used inscene information. Herein, a course is shown by coordinate valuesindicating the two-dimensional position of a block, by dividing thestrike zone into 3×3, or nine, horizontal and vertical blocks as shownin FIG. 15, where the lower left corner as seen from the batter's sideis the origin, the horizontal direction is the x-axis, and the verticaldirection is the y-axis. A subscript represents the index of a scene.Next, using the probability distribution p(s) for the course and thedynamics p(s_(t)|s_(t−1)) of transition of the course, course (x₂, y₂)for the second pitch is decided by random sampling from p(s)p(s₂|s₁).Subsequently, using the probability distribution p(s) for the course andthe dynamics p(s_(t)|s_(t−1)) of transition of the course, course(x_(t), y_(t)) for the t-th pitch is decided by random sampling fromp(s)p(s_(t)|s_(t−1)) in a similar manner.

The speed and the pitch type may be decided simultaneously when thepresentation trajectory decision unit 25 decides the presentationtrajectory with reference to the trajectory database and thus notdecided by the presentation sequence generation unit 24, or may bedecided by the presentation sequence generation unit 24 based on priorprobability and dynamics as with the course.

When the presentation sequence generation unit 24 has decided all ofmultiple parameters relating to the flying of the flying object (forexample, course, speed, and pitch type) by random sampling, thetrajectory database may be checked to see if there is any trajectorydata similar to the scene. If there is no trajectory data similar to thescene decided by random sampling, some of the multiple parametersrelating to the flying of the flying object may be randomly sampledpreferentially and parameters may be decided so that similar trajectorydata is present. In doing so, which one of the parameters is givenpriority is predefined in accordance with the practice goal. Such aconfiguration allows generation of a scene close to real pitching,enhancing the reality of experience.

It is also possible for the presentation sequence generation unit 24 tocontrol the prior probability p(s) and the dynamics p(s_(t+1)|s_(t))based on the practice goal received from the practice goal acquisitionunit 23. This can realize 1. practice of course distinction, 2. practicefor enhancing speed change, and 3. practice for enhancing pitch typechange, for example. They will be individually described in detail.

1. The practice of course distinction is practice for distinguishingbetween an outside strike and a ball, for example. For example, as shownin FIG. 19, the probability distribution of prior probability p(s) maybe bimodal: a strike (a course for which a batter may swing) and a ball(a course for which a batter should not swing). For the dynamicsp(s_(t+1)|s_(t)), only the course is decided first, then the pitch typeand the speed are decided by random sampling based on p(pitch type,speed|course).

2. For the practice for enhancing speed change, dynamicsp(s_(t+1)|s_(t)) is defined with speed; the speed is decided asp(s_(t+1)|s_(t)), and then the course and the pitch type are decided byrandom sampling based on p(course, pitch type|speed).

3. For the practice for enhancing pitch type change, the dynamicsp(s_(t+1)|s_(t)) is defined with the pitch type; the pitch type isdecided as p(s_(t+1)|s_(t)), and then the course and speed are decidedby random sampling based on p(course, speed|pitch type). However, asspeed and pitch type generally have high correlation, it substantiallyhas high similarity to the practice for enhancing speed change.

The prior probability distribution and the dynamics may also be decidedbased on actually pitched balls. For example, the prior probabilitydistribution may be determined from an average of pitches of aparticular player and the dynamics may be determined from the pitchtransition of the player, or the prior probability distribution may bedetermined from an average of pitches of all pitchers and the dynamicsmay be determined from the pitch transition of the player in question.

The presentation sequence generation unit 24 generates each piece ofscene information as described above and repeats this as many times asthe number of scenes (pitches), thereby generating a presentationsequence. The generated presentation sequence is sent to thepresentation trajectory decision unit 25.

At step S23, the presentation trajectory decision unit 25 receives thepresentation sequence from the presentation sequence generation unit 24,selects most similar trajectory data from the trajectory database foreach of the scenes included in the presentation sequence so as to decidea presentation trajectory representing the motion of a flying object,and outputs the decided presentation trajectory in association with thepresentation sequence. A presentation trajectory DB_I is selected usingthe formula below.

${DB\_ I} = {{\underset{i}{\arg\;\min}{E( {{{course}\mspace{14mu} q} - {{course}\mspace{14mu}{DB}_{i}}} )}} + {E( {{{pitch}\mspace{14mu}{type}\mspace{14mu} q} - {{pitch}\mspace{14mu}{type}\mspace{14mu}{DB}_{i}}} )} + {E( {{{speed}\mspace{14mu} q} - {{speed}\mspace{14mu}{DB}_{i}}} )}}$

Here, q represents scene information included in a presentationsequence, and DB_(i) represents trajectory data contained in thetrajectory database. That is, “course q” is the course for a certainscene, and “course DB_(i)” is the course for the i-th trajectory data.The presentation trajectory decision unit 25 outputs information thatassociates the presentation trajectory DB_I with the presentationsequence (hereinafter referred to as trajectory-added presentationsequence).

At step S24, the presentation action decision unit 26 receives thetrajectory-added presentation sequence from the presentation trajectorydecision unit 25, and selects action data from the action database foreach of the scenes included in the trajectory-added presentationsequence, thereby deciding a presentation action representing the motionof the opponent player. Since action data stored in the action databaseis associated with trajectory data stored in the trajectory database ona one-to-one basis, action data identified by the action ID and theopponent player ID which are associated with the presentation trajectoryDB_I is selected as the presentation action. Specifically, thepresentation action decision unit 26 takes information associatingpresentation trajectories DB_I with the presentation sequence as input,retrieves action information corresponding to each DB_I (action ID,opponent player ID, and action video) from the action database andassociates it with the trajectory-added presentation sequence, andoutputs the trajectory-added presentation sequence with which the actiondata has been associated, as a trajectory-and-action-added presentationsequence. The trajectory-and-action-added presentation sequence is sentto the experience synthesis unit 27.

At step S25, the experience synthesis unit 27 receives thetrajectory-and-action-added presentation sequence from the presentationaction decision unit 26, constructs a virtual environment to beexperienced by the user based on the presentation trajectory and thepresentation action included in the trajectory-and-action-addedpresentation sequence, and outputs it.

While any known technique may be employed to construct a virtualenvironment, it can be carried out as follows, for example. First,objects for constituting a virtual environment, such as a ball and astadium, are referred to as constituent materials, and computer graphics(CG) data for reproducing each such constituent material in a virtualenvironment are prestored as virtual environment material. A virtualenvironment material is not limited to CG data but may also be a movingimage or still image data clipped from an actually captured video.Position and posture information relating to a constituent material isprestored as well. Here, the position and posture information isinformation including position information in the same coordinate systemas a presentation trajectory and posture information in that coordinatesystem. The experience synthesis unit 27 reads virtual environmentmaterials to be arranged in a virtual environment, and arranges thevirtual environment material of a static object, which does nottemporally change, in the virtual environment in accordance with itsposition and posture information. At the same time, the experiencesynthesis unit 27 arranges the virtual environment material of a dynamicobject involving temporal change, such as an opponent player or a flyingobject, in the virtual environment based on the presentation trajectoryand the presentation action associated with thetrajectory-and-action-added presentation sequence. For example, if thepresentation trajectory is a time series of three-dimensional positioninformation, a virtual environment material corresponding to the flyingobject is read and arranged at a three-dimensional position and in acertain posture on the virtual environment. Also, if the presentationaction is a video clipped from a video of a real environment, a video ofan opponent player is synthesized at a predetermined position on thevirtual environment. Here, a configuration is also possible whichmeasures the position and posture of the user's head using a motionsensor or the like and controls the line of sight in the virtualenvironment based on the position and posture information of the user.

The experience synthesis unit 27 may receive a practice intensity fromthe practice goal acquisition unit 23 as input and modify the videobased on the practice intensity it received. The practice intensitydecides the difficulty level of practice. However, it is not always thecase that the difficulty level simply increases as the value of practiceintensity becomes greater.

For example, practice intensities are classified with numbers from 1 to6 and each defined as follows:

1. No modification.

2. Display a video of a pitcher as a stick figure (see ReferenceLiterature 2). It has been found that presentation of a human as a stickfigure makes its action appear to be slow. On the other hand, the senseof realism lowers compared to presentation with a live-action video.

-   Reference Literature 2: Ayumi Matsumoto, Dan Mikami, Xiaojun Wu,    Harumi Kawamura, and Akira Kojima, “Multi View Layered GPDM for View    Invariant Human 3D Pose Estimation from Single RGB Camera Input”,    the transactions of the Institute of Electronics, Information and    Communication Engineers, Vol. J97-D, No. 7, July 2014.    3. Randomly shuffle videos. This serves as practice for not being    affected by a preceding action prior to pitching of a ball.    4. Present the same video throughout. This produces a similar effect    to the practice intensity 3.    5. Obscure a part (for example, the source of a ball) by image    processing. This requires the player to judge the pitch at a    position closer to his or her hand.    6. Present no video.

Specifically,

1. Train with a video of a real pitcher who delivered the pitch to betrained;

2. Train with a real pitcher replaced by a stick figure;

3. Train with a video of one of multiple template pitchers prepared;

4. Train all the pitches with the same video of the same pitcher;

5. Train with a video modified so that the pitcher's hand is notvisible;

6. Train with a video showing nothing at the location where the pitchershould be present (only the ball).

For example, consider presentation with a stick figure. In this case,posture estimation is performed for each of the actions registered inthe action database. Posture estimation from a monocular image can beachieved by the approach described in Reference Literature 2, forexample. Reference Literature 2 mentions that motion is perceived to beslow when it is presented as a stick figure. This is presumably becausecognitive burden is reduced as a result of human motions beingsimplified as mere sticks. In a certain respect, this can be consideredas lower practice intensity. On the other hand, the facial expression ordetailed hand motions of the pitcher cannot be viewed because stickfigures are used instead of a video. This means more difficult practicebecause the user confronts reduced information.

Practice intensities 3, 4, 5, and 6 have the same concept. There can beinformation about a ball to be pitched in a motion prior to the actualpitching or serving of the ball. For example, the pitch type can beknown from the form. However, since pitchers practice so that they candeliver a number of pitch types with the identical form, it is desirableto be able to judge only from the ball path and respond without beingaffected by the preceding form. It is thus effective to practice withballs pitched from random forms, balls pitched from an identical form,or even balls that abruptly pop out without any presentation of a videoso that the form cannot be viewed at all, for example.

For practice intensity 3, a single action is randomly selected as thepresentation action from action data for the pitcher in question storedin the action database. For practice intensity 4, a single action israndomly selected from action data for the pitcher in question stored inthe action database, and the same action data is always selected duringthe subsequent practice. Thus, when the practice intensity 4 is set, thesame video will be always selected while a video of the same pitcher isbeing viewed. For practice intensity 5, several methods are availablefor consideration. A first method is one that virtually shows an objectthat blocks the pitcher. A second method is one that applies processingsuch as blurring to a pitcher action registered in the action databasein advance via image processing.

At step S26, the experience presentation unit 28 receives theconstructed virtual environment data from the experience synthesis unit27 and outputs it in a format viewable by the user. The video beingoutput may be a video that sees one direction from a certain viewpointin the virtual environment or a video that allows viewing in alldirections like an omnidirectional video. For instance, in the case ofoutputting a video that sees one direction from a certain viewpoint, aperspective projection camera may be virtually set at a certain positionand a CG model present in the virtual environment space may be projectedonto the image plane of the perspective projection camera. In the caseof outputting an omnidirectional video that allows viewing in the allthe directions from a certain viewpoint, an omnidirectional camera maybe virtually set at the certain viewpoint and a CG model present in thevirtual environment space may be projected onto the image plane of theomnidirectional camera.

With the foregoing configuration, the virtual environment constructiontechnique in the fifth embodiment can construct a virtual environmentfor the user to experience a more demanding environment than a realenvironment based on his or her practice goal during training for asport or situation that involves a flying object from another party.This permits the user to easily experience an environment adapted forhis or her practice goal and can improve the efficiency of practicewithout actually preparing a demanding environment.

According to the virtual environment construction technique in the fifthembodiment, it is possible to construct a virtual environment thatenables experience of a more demanding environment than the realitybased on information obtained from a real environment. This allows aplayer to experience a more demanding environment than a realenvironment beforehand to improve his or her performance in a match.

Sixth Embodiment

In sports, it is very important for improving performance in an actualmatch to experience a video taken from the viewpoint position of aplayer who is actually participating in a match with great sense ofrealism before a match. However, taking video from the location of aplayer during a match is difficult as it hinders play.

The aforementioned Reference Literature 1 describes a system that aimsat improving performance in a match by virtually producing anenvironment close to a match and allowing a player to experience itbeforehand in training of sports and the like. The system described inReference Literature 1 is a system for coaching a football player, inwhich a 360° video from the player's perspective that reproduces thesame environment as a match using virtual reality (VR) technique isviewed on a head mounted display.

In a conventional virtual training method, a video of a scene manuallyselected from prepared video by a coach or a player is viewed. Forefficient training, however, it is important to decide a scene thatshould be intensively practiced in response to a player's motion.

In view of the foregoing, an object of the sixth embodiment is toprovide a video presentation technique capable of deciding a scene to bepresented to the user based on a response of the user.

To accomplish the object, the video presentation apparatus in the sixthembodiment is a video presentation apparatus that presents to a user avideo of another party launching a flying object, the video presentationapparatus including: a user state storage that stores a user staterepresenting a physical behavior of the user and scene informationrepresenting a scene of the other party launching the flying object inassociation with each other; a user state acquisition unit that obtainsa user response, which is a user state occurring as a response to thescene presented to the user; a presentation management unit that obtainspresentation scene information which is scene information associatedwith the user response, from the user state storage; and a videopresentation unit that generates a video to be presented to the userbased on the presentation scene information.

The sixth embodiment aims at improving sports performance throughvirtual experience. Assume here a situation where an action of anotherparty and associated movement of a ball occur in a certain phase of asport, and one is trained for an action to handle it. For example,assume a situation such as a baseball batter hitting a ball thrown by apitcher, a soccer keeper catching a ball kicked by a kicker in a penaltykick, a tennis receiver hitting back a ball hit by a server, or avolleyball receiver receiving a ball hit by a server. Hereinafter, aperson that launches a ball, such as a pitcher, kicker, and server aslisted above, will be referred to as “opponent player” or just “anotherparty”. Also, a video equivalent to a single pitch will be referred toas “scene”. A “scene” may be a video captured in a real environment, ormay be a virtual video created with computer graphics (CG) based oninformation in which three-dimensional position information of an objector person as a subject is chronologically arranged. Alternatively, itmay be a video of a virtual environment in which a live-action video anda CG video are synthesized in combination.

Sports to which the sixth embodiment is applicable are not limited tosports that use a ball, such as those mentioned above. It may beapplicable to sports and situations in general where some object islaunched from another party, such as Frisbee, for example. Hereinafter,an object that is launched by an opponent player, including a ball orFrisbee as described above, will be collectively referred to as “flyingobject”.

The video presentation apparatus in the sixth embodiment is aninformation processing device that, in the case of baseball for example,presents a scene of a pitcher delivering a pitch to the user when theuser enters a signal for requesting a next scene from an input devicesuch as a keyboard. In the case of tennis, it similarly presents a sceneof a server making a serve to the user when the user enters a signal forrequesting a next scene from an input device such as a keyboard. Theuser wears a head mounted display to view the scene presented by thevideo presentation apparatus. The video to be presented on the headmounted display is decided in accordance with the user's physicalstates, such as the position and posture of the user's head.

The video presentation apparatus in the sixth embodiment includes a headmounted display 31, a user state acquisition unit 32, a user statestorage 33, a presentation management unit 34, a video presentation unit35, and a scene information storage 36 as shown in FIG. 20. The videopresentation apparatus may further include a user evaluation acquisitionunit 37 and a user state presentation unit 38. By the video presentationapparatus performing the processes at steps shown in FIG. 21, a videopresentation method in the sixth embodiment is implemented.

The video presentation apparatus is a special device configured byloading of a special program into a known or dedicated computer having acentral processing unit (CPU), main memory (random access memory orRAM), and the like, for example. The video presentation apparatusexecutes various kinds of processing under control of the centralprocessing unit, for example. Data input to the video presentationapparatus and/or data resulting from various kinds of processing arestored in the main memory, for example, and data stored in the mainmemory is read as required to be utilized for other processing. Also, atleast part of the processing components of the video presentationapparatus may be formed of hardware such as an integrated circuit. Thestorages provided in the video presentation apparatus may be formed ofmain memory such as random access memory (RAM), an auxiliary storagedevice formed of a hard disk, optical disk, or a semiconductor memorydevice such as a flash memory, or middleware such as a relationaldatabase or a key value store, for example. The storages provided in thevideo presentation apparatus may be each logically partitioned or theymay be stored in a single physical storage device.

The head mounted display 31 is a device to be worn on the user's headfor viewing video and/or hearing sound. The head mounted display 31 hasa display in an area corresponding to the field of view when worn by theuser and a headset at positions corresponding to the ears, for example.The head mounted display 31 contains various sensors, such as anacceleration sensor or displacement sensor, so that the position andposture of the head can be recognized when the user wears it. Thisenables the head mounted display 31 to present a video aligned with theuser's viewpoint.

The user state storage 33 has stored a user state database therein. Theuser state database is a database that accumulates user statesrepresenting the physical behaviors of the user and scene informationrepresenting scenes to be presented to the user in association with eachother. The user state database is specifically a table composed of viewID, scene ID, a number of views, and user state, as shown in the tablebelow.

TABLE 1 View Scene Number of User ID ID views state 1 2 1 a 2 1 1 b 3 22 c 4 2 3 d 5 1 2 e . . . . . . . . . . . .

The view ID is a unique sequential number that is assigned upon eachviewing of one scene. The scene ID is a number assigned to each scenefor identifying that scene. The number of views is a numerical valuerepresenting the number of times the scene has been viewed. The userstate is time series information representing the physical behavior ofthe user at the time of viewing the scene.

The user state will be described in greater detail. The user state maybe the position and posture of the head, whole body posture, or weighttransfer, for example. The position and posture of the head can beobtained from the head mounted display 31. The whole body posture can beobtained using a motion capture system, such as products from VICON, forexample (see Reference Literature 3). Weight transfer can be obtainedusing a balance evaluation system such as a force plate. Since theposition and posture of the head are essential information for the headmounted display 31 to present a video as mentioned above, the user stateincludes at least the position and posture of the head. Other physicalbehaviors, including whole body posture and weight transfer, can beoptionally added for acquisition of more detailed user states.

-   Reference Literature 3: Vicon Motion Systems Ltd., “Motion Capture    Systems|VICON”, [online], [searched on Oct. 20, 2016], the Internet    <URL: https://www.vicon.com/>

The scene information storage 36 has stored therein a scene informationdatabase. The scene information database is a database accumulatingscene information representing the details of scenes to be presented tothe user. The scene information database is specifically a tablecomposed of scene ID, pitch type, ball speed, path, key bind, andpractice probability as shown in the table below.

TABLE 2 Scene Pitch Ball Key Practice ID type speed Path bindprobability 1 Straight 150 km/h Inside high “z” 0.1 ball 2 Curveball 110km/h Outside low “x” 0.08 3 Straight 135 km/h Middle low “c” 0.03 ball .. . . . . . . . . . . . . . . . .

The scene ID is a number assigned to each scene for identifying thescene. The scene ID is linked with a scene ID in the user statedatabase. Pitch type is the pitch type of a ball pitched in the scene.Ball speed is the speed of a ball pitched in the scene. Path is thecourse of a ball pitched in the scene. Key bind is the type of a keywhich is pressed by the user in a normal mode, which is discussed later.The practice probability is a probability value for use in selecting ascene for presentation in a feedback mode, which is discussed later. Thepractice probability is set so that the total sum across the database is1, and is initialized to be uniform in an initial state.

Referring to FIG. 21, the processing procedure of the video presentationmethod performed by the video presentation apparatus in the sixthembodiment will be described below.

At step S31, the user state acquisition unit 32 of the videopresentation apparatus obtains and outputs a user state representing aphysical behavior of the user. At the same time, the user stateacquisition unit 32 accumulates scene information representing the mostrecently presented scene in association with a user state that wasobtained while the user was viewing that scene in the user statedatabase stored in the user state storage 33. Hereinafter, a user stateexhibited by the user as a response during viewing of the most recentlypresented scene will be referred to as user response. The obtained userresponse is sent to the presentation management unit 34.

If there are multiple user states associated with a certain scene in theuser state database, it means that the user state for that scene is notstable (that is, practice for that scene is insufficient); thus, thepractice probability in the scene information database is increased sothat the scene will be presented more. The practice probability may beincreased in any manner. As an example, the practice probability isincreased by a predefined rate a from the current value. Assuming thatthe current practice probability of scene information for which thepractice probability is increased is x, the practice probability afterbeing increased will be ax. Here, since the sum of the practiceprobabilities of all the scenes is 1+ax−x, the practice probabilities ofall the scenes are multiplied by 1/(1+ax−x) so that the sum is 1. Thevalue of a is about 1.1, for example.

At step S33, the presentation management unit 34 of the videopresentation apparatus decides and outputs scene informationrepresenting the scene to be presented to the user (hereinafter referredto as presentation scene information). The way the presentationmanagement unit 34 decides the presentation scene information isdifferent when in the normal mode and when in the feedback mode. Modesetting is made by manual operation of an input device, such as akeyboard, by the user.

In the normal mode, when the user performs a key entry for requestingthe next scene from an input device such as a keyboard, the presentationmanagement unit 34 obtains and outputs scene information associated withthe entered key in advance from the scene information database stored inthe scene information storage 36. For example, assuming that the sceneinformation shown in Table 2 is stored in the scene informationdatabase, when the user enters “z” key, scene information representing ascene of pitching a 150-km/h straight ball inside high will be output.Here, multiple scenes may be set for one key and settings may be madesuch that a time series of scenes of multiple pitches is presented for asingle key entry.

In the feedback mode, the presentation management unit 34 takes a userresponse obtained by the user state acquisition unit 32 as input, andobtains and outputs scene information associated with the user responsefrom the user state database stored in the user state storage 33. Forexample, assuming the user states shown in Table 1 are stored in theuser state database and the scene information shown in Table 2 is storedin the scene information database, when the user response “c” is input,a scene of pitching a 110-km/h curveball outside low will be presentedto the user.

When multiple scenes are associated with a certain user state in theuser information database, presentation scene information is selectedbased on the practice probability in the scene information database.Here, settings may be made such that the probability of appearance of ascene is varied by aggregating the most recently presented multiplescenes in consideration of connection between the scenes. For example, aball at 140 km/h is perceived to be slow after seeing a ball at 160 km/hbut perceived to be fast immediately after seeing a ball at 100 km/h. Bypresenting multiple scenes as a package taking such continuity intoconsideration, more efficient training becomes possible.

At step S34, based on the presentation scene information obtained by thepresentation management unit 34, the video presentation unit 35 of thevideo presentation apparatus generates a video of the scenecorresponding to that presentation scene information and outputs it tothe head mounted display 31. This enables the user to view the scenebeing presented by the video presentation apparatus via the head mounteddisplay 31. The video for presentation may be a live-action video of ascene of a pitcher's actual pitching captured from the position of thebatter's box, or a video of a virtual environment generated by synthesisof constituent materials based on scene information as follows. First,objects for constituting a virtual environment, such as a ball and astadium, are referred to as constituent materials, and CG data forreproducing each such constituent material in a virtual environment areprestored as virtual environment material. A virtual environmentmaterial is not limited to CG data but may also be a moving image orstill image data clipped from an actually captured video. Position andposture information relating to a constituent material is prestored aswell. The video presentation unit 35 reads virtual environment materialsto be arranged in a virtual environment, and arranges the virtualenvironment material of a static object, which does not temporallychange, in the virtual environment in accordance with its position andposture information. At the same time, the video presentation unit 35arranges the virtual environment material of a dynamic object involvingtemporal change, such as an opponent player or a flying object, in thevirtual environment based on the pitch type, ball speed, and pathspecified in scene information. Here, a configuration is also possiblewhich controls the line of sight in the virtual environment based on theposition and posture of the head obtained by the user state acquisitionunit 32.

Modification 1 of the Sixth Embodiment

In modification 1, a user's self-evaluation for each scene is obtainedand used in selection of a scene for presentation, thereby allowing theuser to more intensively practice a scene that user thinks he or she isnot good at. The video presentation apparatus of modification 1 furtherincludes the user evaluation acquisition unit 37 in addition to theprocessing components of the video presentation apparatus according tothe embodiment.

At step S32, the user evaluation acquisition unit 37 of the videopresentation apparatus obtains a self-evaluation for the immediatelypreceding scene entered by the user from an input device such as akeyboard. Possible values of self-evaluation may be 2-grade evaluationlike done well/failed to do well, or 5-grade evaluation, where integersfrom 1 to 5 are used and a greater value indicates that the user didbetter, for example. The user evaluation acquisition unit 37 adjusts thepractice probability in the scene information database based on theself-evaluation obtained. For example, the practice probability for ascene with low self-evaluation is increased and the practice probabilityfor a scene with high self-evaluation is decreased. As a result, a scenefor which the self-evaluation is low and the user thinks he or she isnot good at will be presented more frequently, while a scene for whichthe self-evaluation is high and the user thinks he or she is good atwill be presented less frequently.

The user evaluation acquisition unit 37 may also estimate an evaluationvalue based on a user state obtained by the user state acquisition unit32, thus eliminating the necessity for input of self-evaluation from theuser. For example, a classifier is learned in advance using user statesfor which the user has manually assigned self-evaluations as learningdata, and the classifier is used to classify an input user state andestimate an evaluation value. In this case, self-evaluations just enoughfor completion of learning have to be collected, so that input ofself-evaluations by the user can be done in a certain amount of time.The certain amount of time may be until an error in learning of userstates obtained converges below a threshold, or may be defined as thefirst thirty pitches. As a user state is chronological transition, alearning machine capable of handling time series information, such as arecurrent neural network, may be employed, or a certain number of userstates may be re-sampled and learned via a support vector machine (SVM)or the like. For example, it is possible to re-sample user states during0.4 seconds before catching of a ball at 30 fps (that is, twelvesamples) and make binary classification into good/poor using a SVM withuser states of a-dimensions (for example, six dimensions for the head'sposition and posture) as input. This enables self-evaluation to beestimated from a user state even without input of self-evaluation fromthe user.

Modification 2 of the Sixth Embodiment

Modification 2 is configured to present an obtained user state to enablethe user to check his or her state. The video presentation apparatus ofmodification 2 further includes the user state presentation unit 38 inaddition to the processing components of the video presentationapparatus according to the embodiment.

At step S35, the user state presentation unit 38 of the videopresentation apparatus outputs a user state obtained by the user stateacquisition unit 32 or a user state accumulated in the user statestorage 33 to the head mounted display 31 or an extrinsic display unit,such as a liquid crystal display, connected to the video presentationapparatus. The user state may be displayed in any manner. For example, amethod presenting the temporal transition of one user state as a timeseries graph (method 1), a method presenting the temporal transition ofpredefined N user states as a time series graph (method 2), and a methodpresenting the temporal transition of predefined N user states as anaverage and a distribution (method 3) can be considered.

FIG. 22A is an example of plotting of transition of a user state (headposture) with the method 1. The vertical axis is an absolute coordinatevalue and the horizontal axis is time. FIG. 22 indicates that anopponent player launched a flying object at the time indicated by“release”. Such visualization enables comparison with other players byvisualization of behavior in the batter's box in the case of baseball,for example. In the case of presenting multiple instances as in themethod 2, multiple graphs like the one in FIG. 22A will follow one afteranother. FIG. 22B is an example of plotting of transition of a userstate (head posture) corresponding to multiple instances by the method3. It is generated by collecting user states corresponding to multipleinstances in response to the same scene and plotting the average and thedistribution of them. It enables analysis such as the behavior largelyvarying and being unstable when the distribution is large, for example.

FIGS. 23 and 24 are exemplary presentation of detailed user state in acase where the user state is the position and posture of the head. Thehead position is plotted on each of the x-axis, y-axis, and z-axiscoordinate values (FIG. 23), and the head posture is plotted on each ofthe x-axis, y-axis, and z-axis rotation angles (FIG. 24). Arranging userstates in these six dimensions for two different players (player A andplayer B) enables comparison and analysis thereof.

The video presentation technique of the sixth embodiment may be combinedwith the virtual environment construction techniques of the first tofifth embodiments.

As the sixth embodiment can decide a scene to be presented to the userbased on the user's response to a certain scene, it enables efficienttraining.

Seventh Embodiment

In a sport match, one sometimes cannot fully exert his or her abilitywhen encountering a first situation he or she has not experiencedpreviously. In baseball, a situation where a player has trouble inhandling a pitcher he or she meets for the first time can be describedby the expression “weak to a first-time opponent”. To address such asituation, it would be effective for the player to experience somepitches of the pitcher from the player's perspective beforehand in thesame environment as an actual match.

It is however virtually difficult to preliminarily experience a nextopponent's pitches in a complete fashion. For preliminarily experiencinga next opponent's pitches, a method for viewing a video of theopponent's past pitches captured from a stand and the like is known;however a video viewed in this method is different from the view seen bya player actually standing in the batter's box in terms of viewpointand/or field of view, thus is not adequate as preliminary experience.

The aforementioned Non-patent Literature 1 discloses a method forrealizing preliminary experience from a player's perspective. In themethod, a camera capable of capturing a 360° panoramic image(hereinafter, referred to as an omnidirectional camera) is installed atthe position of the player's perspective in the batter's box, and theplayer views a video from the player's perspective captured by theomnidirectional camera on a head mounted display.

However, since installation of an omnidirectional camera in the batter'sbox during a match is virtually difficult, the method of Non-patentLiterature 1 is difficult to implement.

As a method for realizing preliminary experience other than that ofNon-patent Literature 1, it is also possible to generate a virtualenvironment that reproduces a real environment entirely with CG, forexample. However, to precisely create CG of players during play, playersactually in play are required to wear accurate sensors; reproducing areal environment entirely with CG is fairly expensive. In contrast,reproducing players with simple CG data is also possible. However, CGdata of reproduced players has unnatural motion and lacks the sense ofrealism, thus not being adequate for preliminary experience.

An object of the seventh embodiment is therefore to provide a virtualenvironment construction apparatus that is capable of easily generatinga virtual environment with great sense of realism.

Assume that a dynamic material which is a material whose positiontransitions and that makes movements, a static material which is amaterial whose position does not transition and that makes no movements,and a special dynamic material which is a material whose position doesnot transition and that makes movements are present in a realenvironment. The virtual environment construction apparatus in theseventh embodiment is a virtual environment construction apparatus thatgenerates a virtual environment reproducing such a real environment. Thevirtual environment construction apparatus according to a first aspectof the seventh embodiment includes a virtual material acquisition unit,a virtual dynamic material position/posture detection unit, a virtualspecial dynamic material generation unit, a synchronization unit, and avirtual environment generation unit.

The virtual material acquisition unit obtains a virtual dynamic materialfor reproducing an object which is a dynamic material on a virtualenvironment and a virtual static material for reproducing a staticmaterial on the virtual environment. The virtual dynamic materialposition/posture detection unit detects the position and posture of thevirtual dynamic material to obtain its time series data. The virtualspecial dynamic material generation unit generates a virtual specialdynamic material for reproducing a human, which is a special dynamicmaterial, on the virtual environment based on a video capturing the realenvironment. The synchronization unit estimates the time of a moment atwhich the human and the object separate from each other by inputting atleast one of a pre-separation image captured before separation betweenthe human and the object and a post-separation image captured afterseparation between the human and the object into a model that haslearned pairs of a video captured around a moment of separation betweenthe human and the object at a high frame rate and the time of the momentof separation between the human and the object, and synchronizes thevirtual dynamic material and the virtual special dynamic material basedon the estimated time. The virtual environment generation unit generatesa virtual environment based on the virtual static material, thesynchronized virtual dynamic material, and the synchronized virtualspecial dynamic material.

The virtual environment construction apparatus according to a secondaspect of the seventh embodiment includes a virtual material acquisitionunit, a virtual dynamic material position/posture detection unit, avirtual special dynamic material generation unit, a synchronizationunit, and a virtual environment generation unit. The virtual materialacquisition unit obtains a virtual dynamic material for reproducing adynamic material on a virtual environment, and a virtual static materialfor reproducing a static material on the virtual environment. Thevirtual dynamic material position/posture detection unit detects theposition and posture of the virtual dynamic material to obtain its timeseries data. The virtual special dynamic material generation unitgenerates a virtual special dynamic material for reproducing a specialdynamic material on the virtual environment based on a video capturing areal environment. The synchronization unit estimates the time of amoment at which a special dynamic material and a dynamic materialseparate from each other by inputting at least one of a pre-separationimage captured before separation between the special dynamic materialand the dynamic material and a post-separation image captured afterseparation between the special dynamic material and the dynamic materialinto a model that has learned pairs of a video captured around a momentof separation between the special dynamic material and the dynamicmaterial at a high frame rate and the time of the moment of separationbetween the special dynamic material and the dynamic material, andsynchronizes the virtual dynamic material and the virtual specialdynamic material based on the estimated time. The virtual environmentgeneration unit generates a virtual environment based on the virtualstatic material, the synchronized virtual dynamic material, and thesynchronized virtual special dynamic material.

A model learning apparatus according to a third aspect of the seventhembodiment learns a model that outputs a time of a moment at which ahuman and an object separate from each other by means of a pair of avideo captured around a moment of separation between the human and theobject at a high frame rate and the time of the moment of separationbetween the human and the object, and using as input at least one of apre-separation image captured before separation between the human andthe object and a post-separation image captured after separation betweenthe human and the object.

A model learning apparatus according to a fourth aspect of the seventhembodiment learns a model that outputs a time of a moment of separationbetween a special dynamic material which is a material whose positiondoes not transition and that makes movements, and a dynamic materialwhich is a material whose position transitions and that makes movements,by means of a pair of a video captured around a moment of separationbetween the special dynamic material and the dynamic material at a highframe rate and the time of the moment of separation between the specialdynamic material and the dynamic material, and using as input at leastone of a pre-separation image captured before separation between thespecial dynamic material and the dynamic material and a post-separationimage captured after separation between the special dynamic material andthe dynamic material.

In this embodiment, a human or an object that really exists, such as apitcher, a ball, or a stadium, will be referred to as material. Amongsuch materials, a material whose position transitions (with time) andthat makes movements (for example, a ball) is referred to as dynamicmaterial, a material whose position does not transition and that doesnot make movements (for example, a stadium, a scoreboard, a spectatorstand) is referred to as static material, and a material whose positionis considered to not transition but that makes movements while stayingat the position (for example, a baseball pitcher or a tennis playerhitting a serve) is referred to as special dynamic material.

Computer graphics data (CG data) for reproducing a material in a virtualenvironment is referred to as virtual material. Among virtual materials,a virtual material for reproducing a dynamic material on a virtualenvironment is referred to as virtual dynamic material, a virtualmaterial for reproducing a static material on a virtual environment isreferred to as virtual static material, and a virtual material forreproducing a special dynamic material on a virtual environment isreferred to as virtual special dynamic material.

As shown in FIG. 25, a virtual environment construction apparatus 4 inthe seventh embodiment includes a virtual material acquisition unit 41,a virtual material storage 41A, a virtual dynamic materialposition/posture detection unit 42, a virtual material position/posturestorage 42A, a virtual special dynamic material generation unit 43, avirtual special dynamic material storage 43A, a synchronization unit 44,a virtual environment generation unit 45, a virtual materialincorporation list storage 45A, and a drawing unit 46.

The virtual material acquisition unit 41 obtains a virtual dynamicmaterial and a virtual static material (S41). As the virtual dynamicmaterial and virtual static material are CG data necessary forgenerating a virtual environment, they are manually input to the virtualmaterial acquisition unit 41 in advance, for example. The virtualdynamic material and virtual static material obtained at step S41 arestored in the virtual material storage 41A.

A dynamic material (for example, a baseball or a tennis ball) iscaptured by a first camera 491 and a second camera 492 shown in FIG. 25,for example. The virtual dynamic material position/posture detectionunit 42 detects the position and posture of the virtual dynamic materialcorresponding to the dynamic material (for example, a path of CG datafor a released baseball on a virtual space, or a path of CG data for aserved tennis ball on a virtual space) to obtain its time series data,based on a video of the dynamic material (for example, a baseball or atennis ball) captured by the first camera 491 and the second camera 492shown in FIG. 25, for example (S42). The position and posture of thevirtual dynamic material detected at step S42 are stored in the virtualmaterial position/posture storage 42A. It is assumed that the virtualmaterial position/posture storage 42A prestores the positions andpostures of virtual static materials and virtual special dynamicmaterials (for example, the positions and postures for CG data of astadium, scoreboard, or pitcher). The positions and postures of virtualstatic materials and virtual special dynamic materials may be manuallyinput in advance.

A special dynamic material (for example, a baseball pitcher or a tennisplayer hitting a serve) is captured by a third camera 493 shown in FIG.25, for example. The virtual special dynamic material generation unit 43generates a virtual special dynamic material based on a video of thespecial dynamic material captured by the third camera 493 shown in FIG.25, for example (S43). It is assumed that the virtual special dynamicmaterial generation unit 43 creates simple CG data using a video of aspecial dynamic material. The details of the CG data generated at stepS43 will be discussed later. The CG data (virtual special dynamicmaterial) generated at step S43 is stored in the virtual special dynamicmaterial storage 43A.

The synchronization unit 44 synchronizes the virtual dynamic materialand the virtual special dynamic material (S44). The details of step S44will be discussed later. The result of the synchronization at step S44is stored in the virtual material position/posture storage 42A.

The virtual environment generation unit 45 generates a virtualenvironment based on the virtual static material, the synchronizedvirtual dynamic material, and the synchronized virtual special dynamicmaterial (S45). The virtual environment generation unit 45 generates avirtual environment by arranging CG data based on position and postureinformation and synchronization information for each virtual material.

The drawing unit 46 draws the generated virtual environment and outputsit as a video such as an omnidirectional video (S46). In the following,the input, output, and processing operation of the individual componentswill be described in detail.

[Virtual Material Acquisition Unit 41]

Input: Virtual static materials, virtual dynamic materials (source: anextrinsic device or the like, not shown)

Output: Virtual static materials, virtual dynamic materials(destination: the virtual material storage 41A)

Processing operation: The virtual material acquisition unit 41 obtainsvirtual static materials and virtual dynamic materials from an extrinsicdevice or the like, and stores the virtual static material and virtualdynamic materials it obtained in the virtual material storage 41A. It isassumed that virtual static materials and virtual dynamic materials areprepared in advance and input to the virtual material acquisition unit41.

[Virtual Material Storage 41A]

Input: Virtual static materials, virtual dynamic materials (source: thevirtual material acquisition unit 41)

Output: Virtual static materials, virtual dynamic materials(destination: the virtual environment generation unit 45)

Processing operation: The virtual material storage 41A stores thevirtual static materials and virtual dynamic materials obtained by thevirtual material acquisition unit 41 in association with virtualmaterial IDs, and outputs virtual static materials and virtual dynamicmaterials in accordance with a request from the virtual environmentgeneration unit 45. Specific examples of virtual static materialsinclude CG data for a stadium in the case of baseball or CG data for atennis court in the case of tennis. Specific examples of virtual dynamicmaterials include CG data for a baseball in the case of baseball or atennis ball in the case of tennis.

[Virtual Dynamic Material Position/Posture Detection Unit 42]

Input: An output value of a sensor (a camera) (source: the first camera491, the second camera 492, for example)

Output: The position and posture of a virtual dynamic material at eachtime (destination: the virtual material position/posture storage 42A)

Processing operation: The virtual dynamic material position/posturedetection unit 42 estimates the position and posture of a dynamicmaterial in the real environment based on an output value of a sensor (acamera), detects the position and posture of a virtual dynamic materialcorresponding to the dynamic material on a virtual space at each timebased on the result of estimation, and obtains its time series data.

As mentioned above, multiple cameras (for example, the first camera 491,the second camera 492) can be utilized as sensors for estimating thethree-dimensional position and posture of a dynamic material. A specificexample of an approach that utilizes multiple cameras to computethree-dimensional position information of an object is one that employstriangulation. Specifically, for videos captured by a camera group thathave undergone camera calibration in advance, the position of an objecton the images is determined. Here, the position of the object on animage may be manually given, or the object may be detected via adetection approach such as template matching, and the center positionthereof may be set as the position of the object. By applyingtriangulation using the positions detected on the images and cameraparameters determined in camera calibration, the three-dimensionalposition of the object can be determined.

For posture information, to how much extent the object is rotatedrelative to a reference posture can be determined from details of thesurface of the object captured (for example, stitches or a pattern on aball). Another example of a sensor for determining the position andposture of a dynamic material can be a Doppler radar. As the Dopplerradar is a well-known technique, detailed description of the Dopplerradar is omitted. Any other sensors and approaches that are capable ofobtaining three-dimensional position and posture information of anobject may be used. Note that the position and posture of the dynamicmaterial (for example, a baseball) estimated at step S42 are convertedin the same step to a position and a posture of a corresponding virtualdynamic material (for example, CG data for the baseball) on a virtualspace, and time series data relating to the position and posture of thevirtual dynamic material is output.

[Virtual Material Position/Posture Storage 42A]

Input: Position and posture information and synchronization informationfor a virtual material (source: the virtual dynamic materialposition/posture detection unit 42, the synchronization unit 44)

Output: Position and posture information and synchronization informationfor the virtual material (destination: the synchronization unit 44, thevirtual environment generation unit 45)

Processing operation: The virtual material position/posture storage 42Astores position and posture information and synchronization informationfor each virtual material. The virtual material position/posture storage42A stores time series data obtained by the virtual dynamic materialposition/posture detection unit 42 as the position and posture of thevirtual dynamic material at each time. In contrast, for position andposture information relating to static materials and special dynamicmaterials, whose position does not transition with time, such as astadium, a ground, or a pitcher, the virtual material position/posturestorage 42A stores data prepared in advance. Specifically, in thevirtual material position/posture storage 42A, a virtual materialposition/posture information table (see FIG. 27) composed of recordsrepresenting three-dimensional position and posture information of eachvirtual material at each time is stored.

The virtual material position/posture information table has a “materialID” uniquely identifying a material, a “virtual material ID” uniquelyidentifying a virtual material, and “position” and “posture” values ofthe virtual material at each “time”, as shown in FIG. 27. The positionis represented as a three-dimensional translation vector and the postureis represented as a three-dimensional vector representing a rotationangle with respect to each axis. For example, assuming baseballpitching, if material Oi represents a straight ball, virtual material Eicorresponding to the material Oi is CG data for a baseball stored in thevirtual material storage 41A. Then, the position and posturecorresponding to each time represent at which position on a virtualspace and in which posture the CG data for a baseball is present at thattime. More specifically, positions Ti(1), . . . , Ti(ti) represent apath of the CG data (virtual material Ei) for a baseball on a virtualspace, and postures Ri(1), . . . , Ri(ti) represent how the CG data(virtual material Ei) for the baseball rotates on the virtual space. InFIG. 27, a virtual material with “-” stored in the time means that it isa virtual static material or a virtual special dynamic material, whoseposition or posture does not transition with time, such as a stadium anda pitcher. It is assumed that position and posture information of such avirtual material with no transition of position or posture is prestored.Also, a time defined for a virtual material represents the time elapsedsince when the virtual material was incorporated into a virtualenvironment by the virtual environment generation unit 45, which isdiscussed later. Specifically, if the virtual environment generationunit 45 incorporates the virtual material Ei into the virtualenvironment at time ta, the position and posture of the virtual materialEi at time (ta+1) will be Ti(1) and Ri(1) respectively, and the positionand posture of the virtual material Ei at time (ta+2) will be Ti(2) andRi(2) respectively.

[Virtual Special Dynamic Material Generation Unit 43]

Input: Video (source: the third camera 493, for example)

Output: Virtual special dynamic materials (destination: the virtualspecial dynamic material storage 43A)

Processing operation: The virtual special dynamic material generationunit 43 takes a video captured by a camera (for example, the thirdcamera 493) as input, pastes part or the all of the video to prepared CGdata as texture to thereby create CG data based on live action, andoutputs the CG data as a virtual special dynamic material.

As a specific example, FIG. 28 shows the operations of the virtualspecial dynamic material generation unit 43 in the case of generating avirtual special dynamic material of a baseball pitcher.

In the example of FIG. 28, a rectangular plane (a billboard) is utilizedas CG data serving as a base for pasting video. First, the virtualspecial dynamic material generation unit 43 reads video V captured by acamera (for example, the third camera 493) (S131). Assume that the videoV contains a pitcher. The virtual special dynamic material generationunit 43 then clips partial video V′ from the video V (S132). An exampleof the region to be clipped can be a rectangular region containing aregion in which the pitcher is present, for example. The size and/orposition of the rectangular region may either be manually given inadvance by a person viewing the video V or be automatically given. Amethod for automatically giving the size and/or position of therectangular region can be background differential method, for example.Using the background differential method, the region in which thepitcher is present can be determined, and then a rectangular region maybe defined so that it contains the region. Also, the region to beclipped is not limited to a rectangular region; only a region in whichthe pitcher is present may be clipped, for example. The aforementionedbackground differential method or the like can be employed as a methodfor clipping only the region in which the pitcher is present. Processingfor clipping the partial video V′ from the video V may be performed ornot performed. When processing for clipping the partial video V′ is notperformed, it is deemed for the sake of convenience that the video V′has been obtained by clipping a rectangular region of the same size asthe video V. Finally, the virtual special dynamic material generationunit 43 pastes the video V′ on the rectangular plane (billboard) astexture (S133), and outputs the CG data as a virtual special dynamicmaterial to the virtual special dynamic material storage 43A.

[Virtual Special Dynamic Material Storage 43A]

Input: Virtual special dynamic materials (source: the virtual specialdynamic material generation unit 43)

Output: Virtual special dynamic materials (destination: thesynchronization unit 44, the virtual environment generation unit 45)

Processing operation: The virtual special dynamic material storage 43Astores the virtual special dynamic material generated at step S43, andoutputs a virtual special dynamic material to components in accordancewith a request from the components.

[Synchronization Unit 44]

Input: Virtual special dynamic materials (source: the virtual specialdynamic material storage 43A), position and posture information ofvirtual dynamic materials (source: the virtual material position/posturestorage 42A), and position and posture information of virtual specialdynamic materials (source: the virtual material position/posture storage42A)Output: Synchronization information (destination: the virtual materialposition/posture storage 42A)Processing operation: The synchronization unit 44 synchronizes a virtualspecial dynamic material (for example, CG data for a pitcher) and avirtual dynamic material relevant to the virtual special dynamicmaterial (for example, CG data for a ball thrown by a pitcher). Anotherexample of such combination can be CG data for a tennis player and CGdata for a tennis ball served by that player. It is assumed thatcorrespondence between a virtual special dynamic material and a virtualdynamic material is predefined. Synchronization is equivalent todetermining a start time of synchronization between synchronizationmaterials in the virtual material position/posture information table ofFIG. 27.

As a specific example, consider synchronization between CG data for apitcher and CG data for a ball thrown by that pitcher. In this case, invideo V′ pasted to a billboard as texture, the time of a moment at whichthe ball is released from the pitcher's hand may be set as thesynchronization start time of the CG data for a ball as asynchronization material. Here, the time of the moment at which the ballis released from the hand may be determined using any method.

For example, template matching of the ball may be performed for eachtime of the texture (video V′) and the time that is detected first maybe set as the time of moment of ball release, namely the synchronizationstart time. Alternatively, template matching may be performed using atemplate of hand or arm form of the pitcher at the time of release foreach time of the texture (video V′) and the time that is detected firstmay be set as the synchronization start time.

Although the above method presumes that the moment of the pitcherreleasing the ball is captured in video V′, since the speed of swingingof the pitcher's arm is very high, the moment of release might not becaptured in the resulting video V′ at a common frame rate used forcapturing a video (for example, 30 fps, 60 fps). If the moment ofrelease is not captured in the video V′, the time of release may beestimated from images before and after the release, instead ofperforming template matching for a ball, hand, or arm and setting theresulting time as the time of release as described above.

Methods for estimating the time of release from images before and afterthe release include a learning-based approach, for example.Specifically, the moment (time) of release is determined from imagescaptured at a high frame rate (for example, 1000 fps) such that themoment of release is included, and multiple image pairs each consistingof a pre-release image and a post-release image corresponding to pastand future times shifted by a predetermined number of frames relative tothe moment (time) of release are created while varying the number offrames being shifted. Using the multiple image pairs and the moment(time) of release as teacher data, a model for determining the moment(time) of release from an image pair is learned. Using a thus learnedmodel, the moment (time) of release can be estimated when a pair of apre-release image at a low frame rate (also called a first image) and apost-release image at a low frame rate (also called a second image) isgiven. The model may be learned in any manner. For example, a linearclassifier may be applied using coordinate values of a hand in apre-release image and a post-release image, the direction of an arm, theposition of the ball after release, and the like as feature amounts, orDNN may be applied including feature extraction.

Redefining step S44 with more general expression, the synchronizationunit 44 extracts an image pair composed of the first image (apre-release image), which is an image captured before separation (forexample, the release) between a human (for example, a pitcher) and anobject (for example, a ball), and the second image (a post-releaseimage), which is an image captured after separation (for example, therelease) between the human (for example, a pitcher) and the object (forexample, a ball), from a video capturing a real environment (forexample, video V′), matches the image pair against an already learnedmodel to estimate the time at which the human (for example, a pitcher)and an object (for example, a ball) separate from each other (forexample, the moment of release), and synchronizes a virtual dynamicmaterial (for example, CG data for the ball) and a virtual specialdynamic material (for example, CG data for the pitcher) based on theestimated time.

The model used for estimating the time of release from images before andafter the release may be learned by the synchronization unit 44 inadvance and stored therein, or may be learned by an extrinsic modellearning apparatus different from the virtual environment constructionapparatus in advance and stored in the synchronization unit 44.

An example of detection of the time of release using the above-describedmethod is shown in FIG. 29. The synchronization unit 44 performs releasedetermination for all the frames (for every time) of texture (video V′)pasted to CG data for a pitcher. Specifically, the synchronization unit44 executes template matching using a template of a pitcher's hand format the time of release and computes a matching score (S141). If thematching score is equal to or greater than threshold th1 (S142Y, namelyin the case of being similar), the time is set as the synchronizationstart time for the ball (end). The synchronization unit 44 performs theprocessing at step S141 for all the frames (for every time) of video V′,and if a score equal to or greater than threshold th1 is not obtainedfor any of the frames of video V′ (S143Y), the synchronization unit 44executes template matching from the first frame (time) using a balltemplate and computes a matching score (S144). When the matching scoreis equal to or greater than threshold th2 (S145Y), the synchronizationunit 44 sets the first time Ta at which the threshold th2 has beenreached as a post-release time, and sets time Ta−1, one time earlierthan time Ta, as a pre-release time (S146). The synchronization unit 44estimates the time of release using an image pair composed of the firstimage at time Ta−1 and the second image at time Ta, and an alreadylearned model (S146). The threshold th1 and threshold th2 are assumed tobe predefined. The synchronization unit 44 sets the time estimatedthrough the above process as the synchronization start time forsynchronization materials in the virtual material position/postureinformation table shown in FIG. 27.

Redefining the operations at step S141 to S146 in the above-describedflowchart with more general expression, the synchronization unit 44estimates the time of separation (for example, the release) between thehuman (for example, a pitcher) and the object (for example, a ball) byexecuting template matching on a video capturing a real environment (forexample, video V′) using a first template (for example, a hand template)prepared in advance as a template for the human (for example, thepitcher)'s body at the moment of separation between the human (forexample, the pitcher) and the object (for example, the ball) and asecond template (for example, a ball template) prepared in advance as atemplate for the object (for example, the ball) at the moment ofseparation between the human (for example, the pitcher) and the object(for example, the ball), and synchronizes a virtual dynamic material anda virtual special dynamic material based on the estimated time. It isalso possible to use only one of the first template (for example, a handtemplate) and the second template (for example, a ball template).

[Virtual Environment Generation Unit 45]

Input: Virtual static materials (source: the virtual material storage41A), virtual dynamic materials (source: the virtual material storage41A), position and posture information of virtual materials (source: thevirtual material position/posture storage 42A), virtual special dynamicmaterials (source: the virtual special dynamic material storage 43A), avirtual material incorporation list (source: the virtual materialincorporation list storage 45A)Output: Virtual environment data (destination: the drawing unit 46)Processing operation: The virtual environment generation unit 45 readsvirtual static materials and virtual dynamic materials from the virtualmaterial storage 41A, reads position and posture information of eachvirtual material from the virtual material position/posture storage 42A,reads virtual special dynamic material from the virtual special dynamicmaterial storage 43A, and merges them in accordance with the virtualmaterial incorporation list to generate virtual environment data (S45).

The generated virtual environment data is sent to the drawing unit 46.The virtual environment data refers to data for a virtual space in whichone or more virtual materials are arranged in a certain virtual space.The virtual environment generation unit 45 reads a virtual materialincorporation list for generating a virtual environment from the virtualmaterial incorporation list storage 45A. The virtual materialincorporation list has a “virtual material ID” uniquely identifying avirtual material, and an “incorporation start time”, which is the timeat which the virtual material is incorporated into the virtualenvironment. It is assumed that the virtual material incorporation listis manually prepared in advance and prestored in the virtual materialincorporation list storage 45A. The virtual environment generation unit45 incorporates a virtual material into the virtual environment inaccordance with the virtual material incorporation list. In doing so,the virtual environment generation unit 45 reads the position andposture of the virtual material from the virtual materialposition/posture storage 42A and arranges it on the virtual space basedon the position and posture. After the virtual environment generationunit 45 has incorporated all the virtual materials described in virtualmaterial incorporation list into the virtual environment, it endsprocessing.

[Drawing Unit 46]

Input: Virtual environment data (source: the virtual environmentgeneration unit 45)

Output: A video (destination: a video display device (not shown))

Processing operation: The drawing unit 46 draws virtual environment datagenerated at step S45 and outputs it in a state viewable by the user,for example, as a video (S46). The video output by the drawing unit 46may be a video that sees one direction from a certain viewpoint in thevirtual environment or a video that allows viewing in all directionslike an omnidirectional video. For instance, in the case of outputting avideo that sees one direction from a certain viewpoint, a perspectiveprojection camera C may be virtually set at a certain position and CGdata present in the virtual environment space may be projected onto theimage plane of the camera C. Specifically, when T is a position as anextrinsic parameter of the camera C, R is the posture, and K is anintrinsic parameter, a certain point p within the space in which thevirtual environment data exists will be projected as point q on theimage plane of the camera C as follows.q=K(Rp+T)

Here, the intrinsic parameter K is a 3×3 matrix composed of the focaldistance and/or the image center of the camera C.

In the case of outputting an omnidirectional video that allows viewingin all the directions from a certain viewpoint, an omnidirectionalcamera O may be virtually set at the certain viewpoint and CG datapresent in the virtual environment space may be projected onto the imageplane of the camera O. Specifically, when T is a position as anextrinsic parameter of the camera O, R is the posture, W is the width ofthe image plane of projection, and H is the height thereof, a certainpoint p within the space in which the virtual environment data existswill be projected as point q=(q_(x), q_(y))^(T) onto the image plane ofthe camera O as follows.

p^(′) = Rp + T = (p_(x)^(′)p_(y)^(′)p_(z)^(′))^(T)$q_{x} = {( \frac{\theta\; W}{2\pi} ) + \frac{W}{2}}$$q_{y} = \frac{\varphi\; H}{\pi}$where

${\theta = {\arctan( \frac{p_{z}^{\prime}}{p_{x}^{\prime}} )}},{\varphi = {\arccos( \frac{p_{y}^{\prime}}{p^{\prime}} )}}$

While the present example employs equidistant cylindrical projection asa projection for representing an omnidirectional video as atwo-dimensional image, other kinds of projection such as Mercator'sprojection may be employed.

The virtual environment construction apparatus in the seventh embodimentis capable of easily generating a virtual environment with great senseof realism.

Eighth Embodiment

In a sport match, one sometimes cannot fully exert his or her abilitywhen encountering a first situation he or she has not experiencedpreviously. In baseball, a situation where a player has trouble inhandling a pitcher he or she meets for the first time can be describedby the expression “weak to a first-time opponent”. To address such asituation, it would be effective for the player to experience somepitches of the pitcher from the player's perspective beforehand in thesame environment as an actual match.

It is however virtually difficult to preliminarily experience a nextopponent's pitches in a complete fashion. For preliminarily experiencinga next opponent's pitches, a method for viewing a video of theopponent's past pitches captured from a stand and the like is known;however a video viewed in this method is different from the view seen bya player actually standing in the batter's box in terms of viewpointand/or field of view, thus is not adequate as preliminary experience.

The aforementioned Non-patent Literature 1 discloses a method forrealizing preliminary experience from a player's perspective. In themethod, a camera capable of capturing a 360° panoramic image(hereinafter, referred to as an omnidirectional camera) is installed atthe position of the player's perspective in the batter's box, and theplayer views a video from the player's perspective captured by theomnidirectional camera on a head mounted display.

However, since installation of an omnidirectional camera in the batter'sbox during a match is virtually difficult, the method of Non-patentLiterature 1 is difficult to implement.

As a method for realizing preliminary experience other than that ofNon-patent Literature 1, it is also possible to generate a virtualenvironment that reproduces a real environment entirely with CG, forexample. However, to precisely create CG of players during play, playersactually in play are required to wear accurate sensors; reproducing areal environment entirely with CG is fairly expensive. As a method forcreating a virtual environment with great sense of realism in asimplified manner, the Reference Literature 4 below discloses a methodof pasting a live-action video to CG data (a billboard) as texture inthe case of a material that makes complicated motion, like a pitcher.

-   Reference Literature 4: Kunihiko Hayashi and Hideo Saito,    “Synthesizing free-viewpoint images from multiple view videos in    soccer stadium”, IPSJ SIG Technical Report, Information Processing    Society of Japan, May 18, 2006, 2006-CVM-154(24), pp. 173-180

For example, as shown in FIG. 30, imagine a case of generating a virtualenvironment for preliminary experience of a baseball batter 482 standingin a right batter's box 471. In this case, assuming that the pitcher 481is rendered as CG using billboard representation based on a videocaptured by a camera, it is desirable that the angle of the cameracapturing the pitcher 481 coincides with the direction seen by thebatter 482 as much as possible. That is, it would be desirable that thecamera is present on a straight line passing through pitcher 481 and thebatter 482, and that the camera's image capturing direction is parallelwith the straight line passing through the pitcher 481 and the batter482, like a camera 493 a. However, when the pitcher 481 is to becaptured from the position of the camera 493 a during an actual match,the batter 482 would be an occlusion, which leads a problem of increasedsense of inconsistency of CG data created with a video captured by thecamera 493 a. As a way to avoid the occlusion of the batter 482, it isalso possible to use a video captured from a different angle, such as bya camera 493 b; however, since the camera 493 b and the camera 493 ahave different viewpoints, this leads to the problem of increased senseof inconsistency concerning the orientation of the pitcher 481 in CGdata created using a video captured by the camera 493 b.

An object of the eighth embodiment is therefore to provide a virtualenvironment construction apparatus capable of generating a virtualenvironment with low sense of inconsistency.

Assume that a dynamic material which is a material whose positiontransitions and that makes movements, a static material which is amaterial whose position does not transition and that makes no movements,and a special dynamic material which is a material whose position doesnot transition and that makes movements are present in a realenvironment. The virtual environment construction apparatus in theeighth embodiment is a virtual environment construction apparatus thatgenerates a virtual environment reproducing such a real environment. Thevirtual environment construction apparatus in the eighth embodimentincludes a virtual material acquisition unit, a virtual dynamic materialposition/posture detection unit, a preliminary preparation unit, asimilar video retrieval unit, a virtual special dynamic materialgeneration unit, a synchronization unit, and a virtual environmentgeneration unit.

The virtual material acquisition unit obtains a virtual dynamic materialfor reproducing a dynamic material on a virtual environment and avirtual static material for reproducing a static material on the virtualenvironment. The virtual dynamic material position/posture detectionunit detects the position and posture of the virtual dynamic material toobtain its time series data. The preliminary preparation unit associatestime series data obtained in a predefined preliminary preparation phasewith a video of a special dynamic material relevant to the time seriesdata. The similar video retrieval unit retrieves time series data of thepreliminary preparation phase similar to time series data obtained in apredefined virtual environment generation phase, and outputs a video ofa special dynamic material associated with the retrieved time seriesdata. The virtual special dynamic material generation unit generates avirtual special dynamic material for reproducing the special dynamicmaterial on a virtual environment based on the output video of thespecial dynamic material. The synchronization unit synchronizes thevirtual dynamic material and the virtual special dynamic material. Thevirtual environment generation unit generates a virtual environmentbased on the virtual static material, the synchronized virtual dynamicmaterial, and the synchronized virtual special dynamic material.

In the eighth embodiment, a human or an object that really exists, suchas a pitcher, a ball, or a stadium, will be referred to as material.Among such materials, a material whose position transitions (with time)and that makes movements (for example, a ball) is referred to as dynamicmaterial, a material whose position does not transition and that doesnot make movements (for example, a stadium, a scoreboard, a spectatorstand) is referred to as static material, and a material whose positionis considered to not transition but that makes movements while stayingat the position (for example, a baseball pitcher or a tennis playerhitting a serve) is referred to as special dynamic material.

Computer graphics data (CG data) for reproducing a material in a virtualenvironment is referred to as virtual material. Among virtual materials,a virtual material for reproducing a dynamic material on a virtualenvironment is referred to as virtual dynamic material, a virtualmaterial for reproducing a static material on a virtual environment isreferred to as virtual static material, and a virtual material forreproducing a special dynamic material on a virtual environment isreferred to as virtual special dynamic material.

A configuration of the virtual environment construction apparatus 5 inthe eighth embodiment is shown in FIG. 31. In the eighth embodiment, oneor more cameras are provided outside or inside the virtual environmentconstruction apparatus 5. The at least one camera is installed on ornear a straight line connecting between a subject of preliminaryexperience (hereinafter “subject of experience”; for example, the batter482 in FIG. 30) and a subject to be captured in live-action video(hereinafter “image-capturing target”; for example, the pitcher 481 inFIG. 30) and is oriented in the direction of the image-capturing target,like the camera 493 a in FIG. 30. In the example of FIG. 31, the firstcamera 491 and the second camera 492 for capturing dynamic materials anda third camera 493 for capturing special dynamic materials are providedoutside the virtual environment construction apparatus 5, and the thirdcamera 493 is installed on or near a straight line connecting betweenthe subject of experience and the image-capturing target, like thecamera 493 a in FIG. 30. As discussed in more detail later, the firstcamera 491 and the second camera 492 may be replaced with other sensors.

The virtual environment construction apparatus 5 in the eighthembodiment includes a preliminary preparation unit 40, a video storage40A, a virtual material acquisition unit 41, a virtual material storage41A, a virtual dynamic material position/posture detection unit 42, avirtual material position/posture storage 42A, a similar video retrievalunit 47, a virtual special dynamic material generation unit 43, avirtual special dynamic material storage 43A, a synchronization unit 44,a virtual environment generation unit 45, a virtual materialincorporation list storage 45A, and a drawing unit 46.

The operation of the virtual environment construction apparatus 5 in theeighth embodiment will be generally described. The following descriptiontakes baseball as an example, and assumes generation of a virtualenvironment that enables preliminary experience of a game in a rightbatter's box 471 with the batter 482 standing in the right batter's box471, specifically as shown in FIG. 30. In this example, the operationalflow of the virtual environment construction apparatus 5 can be roughlydivided into two phases. One is the preliminary preparation phase. Inthe preliminary preparation phase, a video of the pitcher 481 and thepath of a ball thrown by the pitcher 481 are saved in association witheach other. The other is the virtual environment generation phase. Inthe virtual environment generation phase, virtual materials are combinedto generate a virtual environment.

<Preliminary Preparation Phase>

In the preliminary preparation phase, a dynamic material (a ball) iscaptured by the first camera 491 and the second camera 492 shown in FIG.31, for example. The virtual dynamic material position/posture detectionunit 42 detects the position and posture of a virtual dynamic materialcorresponding to the dynamic material (the path of CG data for areleased ball on a virtual space) and obtains its time series data basedon videos of the dynamic material (the ball) captured by the firstcamera 491 and the second camera 492 shown in FIG. 31, for example(S52A).

A special dynamic material (a pitcher) is captured by the third camera493 shown in FIG. 31, for example. The preliminary preparation unit 40obtains a video of the special dynamic material (the pitcher) capturedby the third camera 493 shown in FIG. 31, for example, and associatesthe time series data obtained at step S42A with a video of the specialdynamic material (pitcher) relevant to it, and stores them in the videostorage 40A (S50).

At step S50, a video of the special dynamic material (the pitcher)including no occlusion is selected. The preliminary preparation unit 40may automatically select such a video or a video including no occlusionmay be manually selected. For example, a video including no occlusioncan be obtained by capturing a pitch from the angle of the camera 493 awhen the batter 482 is in the left batter's box 472. At step S42A, timeseries data corresponding to the special dynamic material (the pitcher)including no occlusion is obtained, and they are stored in the videostorage 40A at step S50 in association with each other.

<Virtual Environment Generation Phase>

In the virtual environment generation phase, the virtual materialacquisition unit 41 first obtains a virtual dynamic material and avirtual static material (S51). As virtual dynamic materials and virtualstatic materials are CG data necessary for generating a virtualenvironment, they are manually input to the virtual material acquisitionunit 41 in advance, for example. The virtual dynamic material and thevirtual static material obtained at step S51 are stored in the virtualmaterial storage 41A.

A dynamic material (a ball) is captured by the first camera 491 and thesecond camera 492 in the aforementioned manner. The virtual dynamicmaterial position/posture detection unit 42 detects the position andposture of the virtual dynamic material (the path of CG data for abaseball on a virtual space) and obtains its time series data(hereinafter also referred to as path data) as at step S52A (S52B). Theposition and posture of the virtual dynamic material detected at stepS52B (time series data, path data) are stored in the virtual materialposition/posture storage 42A. The time series data (path data) at thispoint will be utilized as a query at step S47, which is discussed later.It is assumed that the virtual material position/posture storage 42Aprestores positions and postures of virtual static materials and virtualspecial dynamic materials (for example, the positions and postures of CGdata for a stadium, a scoreboard, and a pitcher). The positions andpostures of virtual static materials and virtual special dynamicmaterials may also be manually input in advance.

The similar video retrieval unit 47 uses the time series data (pathdata) obtained at step S52B as a query to retrieve time series data(path data) of step S52A similar to it from the video storage 40A, andoutputs a video of the special dynamic material (the pitcher) associatedwith the retrieved time series data (path data) (S57).

The virtual special dynamic material generation unit 43 generates avirtual special dynamic material based on the video of the specialdynamic material output at step S57 (S53). It is assumed that thevirtual special dynamic material generation unit 43 creates simple CGdata using a video capturing the special dynamic material. The detailsof CG data generated at step S53 will be discussed later. The CG data(virtual special dynamic material) generated at step S53 is stored inthe virtual special dynamic material storage 43A.

The synchronization unit 44 synchronizes the virtual dynamic materialand the virtual special dynamic material (S54). The details of step S54will be discussed later. The result of synchronization at step S54 isstored in the virtual material position/posture storage 42A.

The virtual environment generation unit 45 generates a virtualenvironment based on the virtual static material, the synchronizedvirtual dynamic material, and the synchronized virtual special dynamicmaterial (S55). The virtual environment generation unit 45 generates avirtual environment by arranging CG data based on the position andposture information and synchronization information for each virtualmaterial.

The drawing unit 46 draws the generated virtual environment and outputsit as a video such as an omnidirectional video (S56). The relationshipbetween the pitcher and the ball in the above example can be consideredas replaced with a player and a ball (or a shuttlecock or the like) invarious ball sports, such as tennis, volleyball, table tennis, orbadminton. In the following, the input, output, and processing operationof the individual components will be described in detail.

[Preliminary Preparation Unit 40]

Input: Time series data obtained in the preliminary preparation phase(source: the virtual dynamic material position/posture detection unit42), and video V (source: the third camera 493)

Output: Time series data obtained in the preliminary preparation phase(destination: the video storage 40A), and video V (destination: thevideo storage 40A)

Processing operation: The preliminary preparation unit 40 associates thetime series data (path data) for a virtual dynamic material (CG data fora ball) obtained in the preliminary preparation phase with video V of aspecial dynamic material (the pitcher) relevant to it, and stores themin the video storage 40A. It is assumed that video V contains a specialdynamic material (the pitcher) as the image-capturing target. While inthis example time series data (path data) represents a path of a virtualdynamic material (CG data for a ball) on a virtual space, time seriesdata (path data) is not limited to this but may represent a path of adynamic material that really exists (a real ball) on a real space. Asdiscussed later, both a path on a real space and a path on a virtualspace can be detected at step S52A (S52B).

[Video Storage 40A]

Input: Time series data obtained in the preliminary preparation phase(source: the preliminary preparation unit 40), video V (source: thepreliminary preparation unit 40)

Output: Time series data obtained in the preliminary preparation phase(destination: the similar video retrieval unit 47), video V(destination: the similar video retrieval unit 47)

Processing operation: The video storage 40A obtains time series data(path data) and video V from the preliminary preparation unit 40, andstores them in association with each other. The video storage 40Aoutputs corresponding video V in accordance with a request (a query)from the similar video retrieval unit 47. Here, time series data similarto the query may be output together.

Specifically, the video storage 40A has stored therein a videoinformation table composed of records relating to individual videos (seeFIG. 33). As shown in FIG. 33, the video information table has a “videoID” uniquely identifying a video, a “relevant dynamic material ID” whichis the ID of a dynamic material relevant to the video, and “position”and “posture” values at each “time”. Notations of time, position, andposture are the same as in the virtual material position/postureinformation table discussed later. As an example of a video and adynamic material relevant to it, if a pitcher is the subject to becaptured in a video, then a dynamic material relevant to it will be aball thrown by the pitcher. Such a correspondence is predefined inaccordance with a virtual environment to be generated.

[Virtual Material Acquisition Unit 41]

Input: Virtual static materials, virtual dynamic materials (source: anextrinsic device or the like, not shown)

Output: Virtual static materials, virtual dynamic materials(destination: the virtual material storage 41A)

Processing operation: The virtual material acquisition unit 41 obtainsvirtual static materials and virtual dynamic materials from an extrinsicdevice or the like, and stores the virtual static material and virtualdynamic materials it obtained in the virtual material storage 41A. It isassumed that virtual static materials and virtual dynamic materials areprepared in advance and input to the virtual material acquisition unit41.

[Virtual Material Storage 41A]

Input: Virtual static materials, virtual dynamic materials (source: thevirtual material acquisition unit 41)

Output: Virtual static materials, virtual dynamic materials(destination: the virtual environment generation unit 45)

Processing operation: The virtual material storage 41A stores thevirtual static materials and virtual dynamic materials obtained by thevirtual material acquisition unit 41 in association with virtualmaterial IDs, and outputs virtual static materials and virtual dynamicmaterials in accordance with a request from the virtual environmentgeneration unit 45. Specific examples of virtual static materialsinclude CG data for a stadium in the case of baseball or CG data for atennis court in the case of tennis. Specific examples of virtual dynamicmaterials include CG data for a baseball in the case of baseball or atennis ball in the case of tennis.

[Virtual Dynamic Material Position/Posture Detection Unit 42]

Input: An output value of a sensor (a camera) (source: the first camera491, the second camera 492, for example)

Output: The position and posture of a virtual dynamic material at eachtime (destination: the virtual material position/posture storage 42A)

Processing operation: The virtual dynamic material position/posturedetection unit 42 estimates the position and posture of a dynamicmaterial in the real environment based on an output value of a sensor (acamera), detects the position and posture of a virtual dynamic materialcorresponding to the dynamic material on a virtual space at each timebased on the result of estimation, and obtains its time series data.

As mentioned above, multiple cameras (for example, the first camera 491,the second camera 492) can be utilized as sensors for estimating thethree-dimensional position and posture of a dynamic material. A specificexample of an approach that utilizes multiple cameras to computethree-dimensional position information of an object is one that employstriangulation. Specifically, for videos captured by a camera group thathave undergone camera calibration in advance, the position of an objecton the images is determined. Here, the position of the object on animage may be manually given, or the object may be detected via adetection approach such as template matching, and the center positionthereof may be set as the position of the object. By applyingtriangulation using the positions detected on the images and cameraparameters determined in camera calibration, the three-dimensionalposition of the object can be determined.

For posture information, to how much extent the object is rotatedrelative to a reference posture can be determined from details of thesurface of the object captured (for example, stitches or a pattern on aball). Another example of a sensor for determining the position andposture of a dynamic material can be a Doppler radar. As the Dopplerradar is a well-known technique, detailed description of the Dopplerradar is omitted. Any other sensors and approaches that are capable ofobtaining three-dimensional position and posture information of anobject may be used. Note that the position and posture of the dynamicmaterial (for example, a baseball) estimated at step S52B are convertedin the same step to a position and a posture of a corresponding virtualdynamic material (for example, CG data for the baseball) on a virtualspace, and time series data relating to the position and posture of thevirtual dynamic material is output.

[Virtual Material Position/Posture Storage 42A]

Input: Position and posture information and synchronization informationfor a virtual material (source: the virtual dynamic materialposition/posture detection unit 42, the synchronization unit 44)

Output: Position and posture information and synchronization informationfor the virtual material (destination: the synchronization unit 44, thevirtual environment generation unit 45)

Processing operation: The virtual material position/posture storage 42Astores position and posture information and synchronization informationfor each virtual material. The virtual material position/posture storage42A stores time series data obtained by the virtual dynamic materialposition/posture detection unit 42 as the position and posture of thevirtual dynamic material at each time. In contrast, for position andposture information relating to static materials and special dynamicmaterials, whose position does not transition with time, such as astadium, a ground, or a pitcher, the virtual material position/posturestorage 42A stores data prepared in advance. Specifically, in thevirtual material position/posture storage 42A, a virtual materialposition/posture information table (see FIG. 35) composed of recordsrepresenting three-dimensional position and posture information of eachvirtual material at each time is stored.

The virtual material position/posture information table has a “materialID” uniquely identifying a material, a “virtual material ID” uniquelyidentifying a virtual material, and “position” and “posture” values ofthe virtual material at each “time”, as shown in FIG. 35. The positionis represented as a three-dimensional translation vector and the postureis represented as a three-dimensional vector representing a rotationangle with respect to each axis. For example, assuming baseballpitching, if material Oi represents a straight ball, virtual material Eicorresponding to the material Oi is CG data for a baseball stored in thevirtual material storage 41A. Then, the position and posturecorresponding to each time represent at which position on a virtualspace and in which posture the CG data for a baseball is present at thattime. More specifically, positions Ti(1), . . . , Ti(ti) represent apath of the CG data (virtual material Ei) for a baseball on a virtualspace, and postures Ri(1), . . . , Ri(ti) represent how the CG data(virtual material Ei) for the baseball rotates on the virtual space. InFIG. 35, a virtual material with “-” stored in the time means that it isa virtual static material or a virtual special dynamic material, whoseposition or posture does not transition with time, such as a stadium anda pitcher. It is assumed that position and posture information of such avirtual material with no transition of position or posture is prestored.Also, a time defined for a virtual material represents the time elapsedsince when the virtual material was incorporated into a virtualenvironment by the virtual environment generation unit 45, which isdiscussed later. Specifically, if the virtual environment generationunit 45 incorporates the virtual material Ei into the virtualenvironment at time ta, the position and posture of the virtual materialEi at time (ta+1) will be Ti(1) and Ri(1) respectively, and the positionand posture of the virtual material Ei at time (ta+2) will be Ti(2) andRi(2) respectively.

[Similar Video Retrieval Unit 47]

Input: Time series data obtained in the preliminary preparation phase(source: the video storage 40A), and video V (source: the video storage40A)

Output: Video V (destination: the virtual special dynamic materialgeneration unit 43)

Processing operation: An exemplary processing flow of the similar videoretrieval unit 47 is shown in FIG. 36. The similar video retrieval unit47 reads time series data (path data) from the virtual materialposition/posture storage 42A (S151). The similar video retrieval unit 47reads time series data (path data) from the video storage 40A (S152).The similar video retrieval unit 47 calculates the similarity betweenthe two pieces of time series data (path data) (S153). The similarity ofthe time series data (path data) at step S153 may be calculated in anyway. For example, when the initial velocity of the ball computed fromtrajectory data i is vs(i), the final velocity is ve(i), the position atwhich the initial velocity is calculated is Ps(i), the position at whichthe final velocity is calculated is Pe(i), and acceleration is A(i), thesimilarity Sij between trajectory data i and trajectory data j isdefined as:Sij=kvs*|vs(i)−vs(j)|+kve*|ve(i)−ve(j)|+kps*|Ps(i)−Ps(j)|+kpe*|Pe(i)−Pe(j)|+ka*|A(i)−A(j)|where vs(i), ve(i), Ps(i), Pe(i), and A(i) are all three-dimensionalvectors, and |⋅| represents norm. Further, kvs, kve, kps, kpe, and kaare coefficients for the respective three-dimensional vectors and arepredefined.

Next, the similar video retrieval unit 47 determines whether all thetime series data (path data) have been read or not (S154). If all thetime series data (path data) have not been read (S154N), the processingreturns to step S152. If all the time series data (path data) have beenread (S154Y), one piece of path data is selected based on thesimilarities calculated at step S153 repeatedly executed thus far, andvideo V corresponding to that path data is read from the video storage40A (S155). The path data may be selected in any manner. For example,path data with the highest similarity may be selected. Alternatively, acertain threshold may be defined and random path data may be selectedfrom pieces of path data having similarity equal to or greater than thethreshold. Finally, the similar video retrieval unit 47 outputs thevideo V it read out to the virtual special dynamic material generationunit 43 (S156).

[Virtual Special Dynamic Material Generation Unit 43]

Input: Video V (source: similar video retrieval unit 47)

Output: Virtual special dynamic materials (destination: the virtualspecial dynamic material storage 43A)

Processing operation: The virtual special dynamic material generationunit 43 takes a video V output by the similar video retrieval unit 47 asinput, pastes part or the all of the video to prepared CG data astexture to thereby create CG data based on live action, and outputs theCG data as a virtual special dynamic material.

As a specific example, FIG. 37 shows the operations of the virtualspecial dynamic material generation unit 43 in the case of generating avirtual special dynamic material of a baseball pitcher.

In the example of FIG. 37, a rectangular plane (a billboard) is utilizedas CG data serving as a base for pasting video. First, the virtualspecial dynamic material generation unit 43 obtains the video V outputby the similar video retrieval unit 47 (S161). The virtual specialdynamic material generation unit 43 then clips partial video V′ from thevideo V (S162). An example of the region to be clipped can be arectangular region containing a region in which the pitcher is present,for example. The size and/or position of the rectangular region mayeither be manually given in advance by a person viewing the video V orbe automatically given. A method for automatically giving the sizeand/or position of the rectangular region can be background differentialmethod, for example. Using the background differential method, theregion in which the pitcher is present can be determined, and then arectangular region may be defined so that it contains the region. Also,the region to be clipped is not limited to a rectangular region; only aregion in which the pitcher is present may be clipped, for example. Theaforementioned background differential method or the like can beemployed as a method for clipping only the region in which the pitcheris present. Processing for clipping the partial video V′ from the videoV may be performed or not performed. When processing for clipping thepartial video V′ is not performed, it is deemed for the sake ofconvenience that the video V′ has been obtained by clipping arectangular region of the same size as the video V. Finally, the virtualspecial dynamic material generation unit 43 pastes the video V′ on therectangular plane (billboard) as texture (S163), and outputs the CG dataas a virtual special dynamic material to the virtual special dynamicmaterial storage 43A.

[Virtual Special Dynamic Material Storage 43A]

Input: Virtual special dynamic materials (source: the virtual specialdynamic material generation unit 43)

Output: Virtual special dynamic materials (destination: thesynchronization unit 44, the virtual environment generation unit 45)

Processing operation: The virtual special dynamic material storage 43Astores the virtual special dynamic material generated at step S43, andoutputs a virtual special dynamic material to components in accordancewith a request from the components.

[Synchronization unit 44]

Input: Virtual special dynamic materials (source: the virtual specialdynamic material storage 43A), position and posture information ofvirtual dynamic materials (source: the virtual material position/posturestorage 42A), and position and posture information of virtual specialdynamic materials (source: the virtual material position/posture storage42A)Output: Synchronization information (destination: the virtual materialposition/posture storage 42A)Processing operation: The synchronization unit 44 synchronizes a virtualspecial dynamic material (for example, CG data for a pitcher) and avirtual dynamic material relevant to the virtual special dynamicmaterial (for example, CG data for a ball thrown by a pitcher). Anotherexample of such combination can be CG data for a tennis player and CGdata for a tennis ball served by that player. It is assumed thatcorrespondence between a virtual special dynamic material and a virtualdynamic material is predefined. Synchronization is equivalent todetermining a start time of synchronization between synchronizationmaterials in the virtual material position/posture information table ofFIG. 35.

As a specific example, consider synchronization between CG data for apitcher and CG data for a ball thrown by that pitcher. In this case, invideo V′ pasted to a billboard as texture, the time of a moment at whichthe ball is released from the pitcher's hand may be set as thesynchronization start time of the CG data for a ball as asynchronization material. Here, the time of the moment at which the ballis released from the hand may be determined using any method.

For example, template matching of the ball may be performed for eachtime of the texture (video V′) and the time that is detected first maybe set as the time of moment of ball release, namely the synchronizationstart time. Alternatively, template matching may be performed using atemplate of hand or arm form of the pitcher at the time of release foreach time of the texture (video V′) and the time that is detected firstmay be set as the synchronization start time.

Although the above method presumes that the moment of the pitcherreleasing the ball is captured in video V′, since the speed of swingingof the pitcher's arm is very high, the moment of release might not becaptured in the resulting video V′ at a common frame rate used forcapturing a video (for example, 30 fps, 60 fps). If the moment ofrelease is not captured in the video V′, the time of release may beestimated from images before and after the release, instead ofperforming template matching for a ball, hand, or arm and setting theresulting time as the time of release as described above.

Methods for estimating the time of release from images before and afterthe release include a learning-based approach, for example.Specifically, the moment (time) of release is determined from imagescaptured at a high frame rate (for example, 1000 fps) such that themoment of release is included, and multiple image pairs each consistingof a pre-release image and a post-release image corresponding to pastand future times shifted by a predetermined number of frames relative tothe moment (time) of release are created while varying the number offrames being shifted. Using the multiple image pairs and the moment(time) of release as training data, a model for determining the moment(time) of release from an image pair is trained. Using a thus trainedmodel, the moment (time) of release can be estimated when a pair of apre-release image at a low frame rate (also called a first image) and apost-release image at a low frame rate (also called a second image) isgiven. The model may be trained in any manner. For example, a linearclassifier may be applied using coordinate values of a hand in apre-release image and a post-release image, the direction of an arm, theposition of the ball after release, and the like as feature amounts, orDNN may be applied including feature extraction.

Redefining step S54 with more general expression, the synchronizationunit 44 extracts an image pair composed of the first image (apre-release image), which is an image captured before separation (forexample, the release) between a human (for example, a pitcher) and anobject (for example, a ball), and the second image (a post-releaseimage), which is an image captured after separation (for example, therelease) between the human (for example, a pitcher) and the object (forexample, a ball), from a video capturing a real environment (forexample, video V′), matches the image pair against an already trainedmodel to estimate the time at which the human (for example, a pitcher)and an object (for example, a ball) separate from each other (forexample, the moment of release), and synchronizes a virtual dynamicmaterial (for example, CG data for the ball) and a virtual specialdynamic material (for example, CG data for the pitcher) based on theestimated time.

The model used for estimating the time of release from images before andafter the release may be trained by the synchronization unit 44 inadvance and stored therein, or may be trained by an extrinsic modellearning apparatus different from the virtual environment constructionapparatus in advance and stored in the synchronization unit 44.

An example of detection of the time of release using the above-describedmethod is shown in FIG. 38. The synchronization unit 44 performs releasedetermination for all the frames (for every time) of texture (video V′)pasted to CG data for a pitcher. Specifically, the synchronization unit44 executes template matching using a template of a pitcher's hand format the time of release and computes a matching score (S171). If thematching score is equal to or greater than threshold th1 (S172Y, namelyin the case of being similar), the time is set as the synchronizationstart time for the ball (end). The synchronization unit 44 performs theprocessing at step S171 for all the frames (for every time) of video V′,and if a score equal to or greater than threshold th1 is not obtainedfor any of the frames of video V′ (S173Y), the synchronization unit 44executes template matching from the first frame (time) using a balltemplate and computes a matching score (S174). When the matching scoreis equal to or greater than threshold th2 (S175Y), the synchronizationunit 44 sets the first time Ta at which the threshold th2 has beenreached as a post-release time, and sets time Ta−1, one time earlierthan time Ta, as a pre-release time (S176). The synchronization unit 44estimates the time of release using an image pair composed of the firstimage at time Ta−1 and the second image at time Ta, and an alreadylearned model (S176). The threshold th1 and threshold th2 are assumed tobe predefined. The synchronization unit 44 sets the time estimatedthrough the above process as the synchronization start time forsynchronization materials in the virtual material position/postureinformation table shown in FIG. 35.

Redefining the operations at step S171 to S176 in the above-describedflowchart with more general expression, the synchronization unit 44estimates the time of separation (for example, the release) between thehuman (for example, a pitcher) and the object (for example, a ball) byexecuting template matching on a video capturing a real environment (forexample, video V′) using a first template (for example, a hand template)prepared in advance as a template for the human (for example, thepitcher)'s body at the moment of separation between the human (forexample, the pitcher) and the object (for example, the ball) and asecond template (for example, a ball template) prepared in advance as atemplate for the object (for example, the ball) at the moment ofseparation between the human (for example, the pitcher) and the object(for example, the ball), and synchronizes a virtual dynamic material anda virtual special dynamic material based on the estimated time. It isalso possible to use only one of the first template (for example, a handtemplate) and the second template (for example, a ball template).

[Virtual Environment Generation Unit 45]

Input: Virtual static materials (source: the virtual material storage41A), virtual dynamic materials (source: the virtual material storage41A), position and posture information of virtual materials (source: thevirtual material position/posture storage 42A), virtual special dynamicmaterials (source: the virtual special dynamic material storage 43A), avirtual material incorporation list (source: the virtual materialincorporation list storage 45A)Output: Virtual environment data (destination: the drawing unit 46)Processing operation: The virtual environment generation unit 45 readsvirtual static materials and virtual dynamic materials from the virtualmaterial storage 41A, reads position and posture information of eachvirtual material from the virtual material position/posture storage 42A,reads virtual special dynamic material from the virtual special dynamicmaterial storage 43A, and merges them in accordance with the virtualmaterial incorporation list to generate virtual environment data (S55).

The generated virtual environment data is sent to the drawing unit 46.The virtual environment data refers to data for a virtual space in whichone or more virtual materials are arranged in a certain virtual space.The virtual environment generation unit 45 reads a virtual materialincorporation list for generating a virtual environment from the virtualmaterial incorporation list storage 45A. The virtual materialincorporation list has a “virtual material ID” uniquely identifying avirtual material, and an “incorporation start time”, which is the timeat which the virtual material is incorporated into the virtualenvironment. It is assumed that the virtual material incorporation listis manually prepared in advance and prestored in the virtual materialincorporation list storage 45A. The virtual environment generation unit45 incorporates a virtual material into the virtual environment inaccordance with the virtual material incorporation list. In doing so,the virtual environment generation unit 45 reads the position andposture of the virtual material from the virtual materialposition/posture storage 42A and arranges it on the virtual space basedon the position and posture. After the virtual environment generationunit 45 has incorporated all the virtual materials described in virtualmaterial incorporation list into the virtual environment, it endsprocessing.

[Drawing Unit 46]

Input: Virtual environment data (source: the virtual environmentgeneration unit 45)

Output: A video (destination: a video display device (not shown))

Processing operation: The drawing unit 46 draws virtual environment datagenerated at step S55 and outputs it in a state viewable by the user,for example, as a video (S56). The video output by the drawing unit 46may be a video that sees one direction from a certain viewpoint in thevirtual environment or a video that allows viewing in all directionslike an omnidirectional video. For instance, in the case of outputting avideo that sees one direction from a certain viewpoint, a perspectiveprojection camera C may be virtually set at a certain position and CGdata present in the virtual environment space may be projected onto theimage plane of the camera C. Specifically, when T is a position as anextrinsic parameter of the camera C, R is the posture, and K is anintrinsic parameter, a certain point p within the space in which thevirtual environment data exists will be projected as point q on theimage plane of the camera C as follows.q=K(Rp+T)

Here, the intrinsic parameter K is a 3×3 matrix composed of the focaldistance and/or the image center of the camera C.

In the case of outputting an omnidirectional video that allows viewingin all the directions from a certain viewpoint, an omnidirectionalcamera O may be virtually set at the certain viewpoint and CG datapresent in the virtual environment space may be projected onto the imageplane of the camera O. Specifically, when T is a position as anextrinsic parameter of the camera O, R is the posture, W is the width ofthe image plane of projection, and H is the height thereof, a certainpoint p within the space in which the virtual environment data existswill be projected as point q=(q_(x), q_(y))^(T) onto the image plane ofthe camera O as follows.

$\begin{matrix}{p^{\prime} = {{{Rp} + T} = ( {p_{x}^{\prime}p_{y}^{\prime}p_{z}^{\prime}} )^{T}}} \\{q_{x} = {( \frac{\theta\; W}{2\;\pi} ) + \frac{W}{2}}} \\{q_{y} = {\frac{\varphi\; H}{\pi}\mspace{14mu}{where}}} \\{{\theta = {{arc}\;{\tan( \frac{p_{z}^{\prime}}{p_{x}^{\prime}} )}}},} \\{\varphi = {{arc}\;{\cos( \frac{p_{y}^{\prime}}{p^{\prime}} )}}}\end{matrix}$

While the present example employs equidistant cylindrical projection asa projection for representing an omnidirectional video as atwo-dimensional image, other kinds of projection such as Mercator'sprojection may be employed.

The virtual environment construction apparatus in the eighth embodimentcan generate a virtual environment with low sense of inconsistency.

Ninth Embodiment

In sports, it is very important for improving performance in an actualmatch to experience a play from the viewpoint position of a player whois actually participating in a match with great sense of realism beforea match. However, taking video from the location of a player during amatch is difficult as it hinders play.

As a solution to this, there has been an attempt to synthesize a videoas seen from a player's position based on a video captured by a camerainstalled outside a field during a match (see Reference Literature 5,for instance). As a part of the approach, Reference Literature 5describes a methodology to create a part of a space with athree-dimensional model, create another part with a billboard model anda video pasted to the model, and synthesize a video from a desiredviewpoint.

-   Reference Literature 5: Kosuke Takahashi, Dan Mikami, Mariko    Isogawa, and Akira Kojima, “A Study on Virtual Omnidirectional Video    Synthesis from Multiple Cameras”, IEICE technical report, vol. 115,    no. 76, pp. 43-48, June 2015

In a case where part of a space to be synthesized is created withcomputer graphics (CG) and another part is created with a live-actionvideo, and a video from a virtual viewpoint established in the space issynthesized, an object created with CG could be also contained in aregion created with live-action video. In such a case, when viewed fromthe virtual viewpoint, both the CG-created part and the live-action partof the object are drawn, looking unnatural.

Possible solutions include methods such as 1. removing a backgroundportion from the live-action region by an approach such as segmentationto leave only a foreground object so that the background portion doesnot appear in the live-action region, and 2. removing an unwantedlive-action object portion from the live-action region and makingrestoration, for example. Although the method of 1 would be effective toa certain degree, it cannot solve the problem when another object ispresent in the live-action region at a position close to the virtualviewpoint relative to the live-action object.

In view of the foregoing, an object of the ninth embodiment is toimprove the reality in a virtual environment constructed by synthesis ofan object created with CG and an object captured as live action.

To accomplish the object, virtual environment construction apparatus inthe ninth embodiment is a virtual environment construction apparatusthat constructs a virtual environment for viewing by a user based on areal environment in which a plurality of objects are present, thevirtual environment construction apparatus including: a modelconstruction method decision unit that, for at least one of theplurality of objects as a target object, decides a model constructionmethod indicating whether a model of the object is constructed with CGor with a live-action video based on at least one of a sensingdifficulty level and a CG drawing difficulty level of the target object;a state sensing unit that measures a state of the target object in thereal environment; an environment model construction unit that constructsan environment model for drawing in the virtual environment inaccordance with the model construction method for a static object whichdoes not involve temporal change; and a dynamic object construction unitthat constructs a model for drawing in the virtual environment inaccordance with the model construction method for a dynamic object whichinvolves temporal change, and synthesizes the model with the environmentmodel.

The virtual environment construction apparatus in the ninth embodimentincludes a model construction method decision unit 60, a state sensingunit 61, a state storage 62, an environment model construction unit 63,a dynamic object construction unit 64, a viewpoint position/directionacquisition unit 65, a video rendering unit 66, and a video presentationunit 67, as shown in FIG. 39. By the virtual environment constructionapparatus performing the processes at steps shown in FIG. 41, a virtualenvironment construction method in the ninth embodiment is implemented.

The virtual environment construction apparatus is a special deviceconfigured by loading of a special program into a known or dedicatedcomputer having a central processing unit (CPU), main memory (randomaccess memory or RAM), and the like, for example. The virtualenvironment construction apparatus executes various kinds of processingunder control of the central processing unit, for example. Data input tothe virtual environment construction apparatus and/or data resultingfrom various kinds of processing are stored in the main memory, forexample, and data stored in the main memory is read as required to beutilized for other processing. Also, at least part of the processingcomponents of the virtual environment construction apparatus may beformed of hardware such as an integrated circuit. The storages providedin the virtual environment construction apparatus may be formed of mainmemory such as random access memory (RAM), an auxiliary storage deviceformed of a hard disk, optical disk, or a semiconductor memory devicesuch as a flash memory, or middleware such as a relational database or akey value store, for example. The storages provided in the virtualenvironment construction apparatus may be each logically partitioned orthey may be stored in a single physical storage device.

For some object present in a space to be constructed (hereinafterreferred to as target object), the model construction method decisionunit 60 decides a model construction method for the target object basedon at least one of the sensing difficulty level and the CG drawingdifficulty level. The model construction method decision unit 60 mayalso decide the model construction method for the target object based ona discrepancy between an angle of observation and an angle of viewing inaddition to the sensing difficulty level and the CG drawing difficultylevel. A model construction method refers to information that indicateswhether a model of the target object is constructed with CG or with alive-action video. The sensing difficulty level is an indicator ofdifficulty in measuring the states of the target object. Here, statesrefer to those necessary for CG drawing of the target object, includingits position and posture. The CG drawing difficulty level is anindicator of difficulty in drawing the target object with CG. CG in thisembodiment is assumed to be three-dimensional CG The discrepancy betweenthe angle of observation and the angle of viewing is the discrepancybetween the camera position at the time of capturing a live-action videoand the position of the virtual viewpoint of a video presented to theuser.

Drawing of an object with three-dimensional CG in a virtual environmentand drawing by means of a live-action video have their respectiveadvantages and disadvantages. An advantage of drawing withthree-dimensional CG is high freedom of viewpoint setting positionbecause drawing is done based on sensed information, enabling relativelyeasy drawing even in the case of drawing an object whose positionsharply changes in a short time while the user changes his or herviewpoint position and orientation, such as when a baseball is seen froma batter's viewpoint. On the other hand, a disadvantage is that someobjects are difficult to sense and the impression of a synthesized videocan be unnatural (for example, hairs, flapping of clothes, the postureof a person sensed from a remote location, and the like). An advantageof drawing by means of a live-action video is that the impression of asynthesized video is natural. On the other hand, a disadvantage is thata large number of cameras are required for neat synthesis of an objectwhose position sharply changes in a short time. The model constructionmethod decision unit 60 decides an optimal model construction method foreach object taking these advantages and disadvantages into account. Thiscan improve the reality in the finally constructed virtual environment.

Specifically, the model construction method decision unit 60 decides themodel construction method through the following seven steps.

Step 1. Set an object presence range.

Step 2. Set a camera position.

Step 3. Set a virtual viewpoint position.

Step 4. Determine the maximum discrepancy value between the angle ofobservation and the angle of viewing.

Step 5. Determine the sensing difficulty level.

Step 6. Determine the CG drawing difficulty level.

Step 7. Determine the model construction method.

At step 1, the presence range of each object in a space to beconstructed is set. Since in many sports the regions of presence ofindividual objects are fixed due to limitation of rules or the like, itis possible to set presence ranges based on rules. It is also possibleto set the presence ranges of typical objects even if they are notprescribed in rules. Alternatively, in the case of model constructionafter image capturing, presence ranges may be set in accordance with thescene to be subsequently constructed.

The description here considers a baseball ground as the space to beconstructed. FIG. 40 is a diagram of a baseball ground as the target ofconstruction seen from a viewpoint at a vertically upward position. Bythe user specifying the presence range of an object on such anillustration representing the space to be constructed by clicking amouse or the like, the presence range of each object at step 1 can beset. Alternatively, presence ranges may be set by reading ones specifiedat the time of system utilization. Alternatively, a file describingobject presence ranges may be prepared in advance based on the rules andthe file may be specified and read at the time of system utilization.For example, in the case of constructing a pitching scene in baseball,objects may include “pitcher”, “ball”, and the like, for example. Inthis case, for each object, a file containing settings of information onthe object is prepared in advance, the information including the “type”of the object such as “pitcher” or “ball”, the “attribute” of the objectsuch as “rigid body” or “articulated object” (its usage will bediscussed later), “dynamic/static category” indicating whether theobject is a dynamic object or a static object (which may be omitted bybeing linked with the attribute; its usage will be discussed later), andthe “presence range” of the object represented by position information.The model construction method decision unit 60 reads the file and setsthe presence ranges of objects. The contents of the file are manuallyset in advance. For example, when the processing target object is apitcher, a region around the mound is set as the presence range of theobject as shown in FIG. 40. When the processing target object is a ball,a rectangular region connecting between the mound and the home base isset as the presence range of the object as shown in FIG. 40. In theexample of FIG. 40, two-dimensional position coordinates on theillustration are used as position information, with the center of thebatter's box being the origin, the direction of the centerfield screenbeing the y-axis, and the direction orthogonal to the y-axis being thex-axis.

At step 2, the respective positions of multiple cameras installedoutside the space to be constructed are obtained. The camera positionscan be obtained by reading positions specified by the user on anillustration representing the space, like FIG. 40, similarly to theobject presence ranges. Alternatively, a separate, previously preparedfile describing camera positions may be read by the model constructionmethod decision unit 60 to set the camera positions.

At step 3, a range which may be set as a virtual viewpoint is read. Arange which may be set as a virtual viewpoint can be obtained by readinga range specified by the user or a system operator on an illustrationlike FIG. 40, similarly to the object presence ranges. Alternatively, aseparate, previously prepared file describing virtual viewpointpositions may be read by the model construction method decision unit 60to set a range which may be set as a virtual viewpoint.

At step 4, the discrepancy between the angle of observation and theangle of viewing are calculated. The angle of observation and the angleof viewing for an object can be determined using the object presencerange obtained at step 1, the camera positions obtained at step 2, andthe virtual viewpoint position obtained at step 3. For example, FIG.42(A) shows discrepancy θ max between the angle of observation and theangle of viewing for baseball pitching. L1 is a straight line connectingbetween a ball passing over the home base and the camera, L2 is astraight line connecting between a virtual viewpoint located at thecenter of the batter's box and the ball, and the angle formed by thestraight line L1 and the straight line L2 is the discrepancy θ maxbetween the angle of observation and the angle of viewing. FIG. 42(B)shows the discrepancy θ max between the angle of observation and theangle of viewing for a pitcher on a mound.

At step 5, the sensing difficulty level is set for each object. Thesensing difficulty level is read from a sensing difficulty level table,for example. The sensing difficulty level table is a table describingsensing difficulty levels predefined in accordance with the attributesof objects, as shown in the table below. In the example of the tablebelow, the values of sensing difficulty level are set based onattributes such as whether the object is a rigid body or not, whether itis an articulated object or not, and whether it is a plastic object ornot. It is assumed that the attributes of objects have been obtained bybeing read from a file in which “type”, “attribute”, “dynamic/staticcategory”, and “presence range” are set for the individual objects asdescribed in step 1. Alternatively, the attributes of objects may beobtained by the user specifying attributes of each object to beconstructed, for example, by clicking of a mouse.

TABLE 3 Shape complexity Rigid body Articulated object Plastic objectSimple a b c Complicated d e f

At step 6, the CG drawing difficulty level is set for each object. TheCG drawing difficulty level is read from a CG drawing difficulty leveltable, for example. The CG drawing difficulty level table is a tabledescribing CG drawing difficulty levels predefined in accordance withthe attributes of objects, as shown in the table below. In the exampleof the table below, the values of CG drawing difficulty level are setbased on attributes such as whether the object is a rigid body or not,whether it is an articulated object or not, and whether it is a plasticobject or not. The attributes of objects are obtained in a similarmanner to the one described in setting of the sensing difficulty level.

TABLE 4 Shape complexity Rigid body Articulated object Plastic objectSimple g h i Complicated j k l

At step 7, based on the sensing difficulty level, the CG drawingdifficulty level, and the discrepancy between the angle of observationand the angle of viewing, a model construction method for the object isdetermined. For example, when SE is the sensing difficulty level, CM isthe CG drawing difficulty level, and θ max is the discrepancy betweenthe angle of observation and the angle of viewing, determination may bemade such that ifγθ max/(αSE*βCM)>thholds, a model is constructed with CG, otherwise a model is constructedwith a live-action video. Here, th is a threshold, and α, β, and γ arepredetermined parameters. The above formula is only an example and maybe modified in any way as long as it makes determination by comparisonwith a threshold using one or more of the sensing difficulty level, theCG drawing difficulty level, and the discrepancy between the angle ofobservation and the angle of viewing.

Instead of following the foregoing steps, it is also possible to preparea file that predesignates use of either CG or a live-action video foreach object and read the file to decide the model construction method.

For each object present in the space to be constructed, the statesensing unit 61 senses the state of the object in that space. Theobtained state of the object is stored in the state storage 62. The wayof sensing varies depending on the attributes of the target object andthe model construction method for that object. For example, in the caseof sensing position information as a state for CG drawing of a baseball,tennis ball, or the like, it is widely known that ball positioninformation can be obtained via a well-known PITCHf/x system forbaseball or via well-known Hawk-Eye system for tennis.

The environment model construction unit 63 takes as input the states ofobjects stored in the state storage 62, and for a static object withlittle temporal change in position or posture among those objects,constructs an environment model for drawing in a virtual environment inaccordance with the model construction method decided by the modelconstruction method decision unit 60. The constructed environment modelis sent to the dynamic object construction unit 64. For an object forwhich model construction with CG has been decided, a model composed ofthree-dimensional geometry and texture is constructed. Thethree-dimensional geometry may be actually measured, or a typicalgeometry prescribed by rules may be utilized because the size of aplaying field and the like are defined by rules in many sports. For anobject for which model construction with a live-action video has beendecided, a live-action video captured by a camera is utilized toconstruct a model.

The dynamic object construction unit 64 takes the states of objectsstored in the state storage 62 as input, and for a dynamic objectinvolving temporal change in position or posture among those objects,constructs a model for drawing in the virtual environment in accordancewith the model construction method decided by the model constructionmethod decision unit 60 based on its state stored in the state storage62. The model constructed for the dynamic object is synthesized with theenvironment model constructed by the environment model construction unit63. This results in construction of the virtual environment forpresentation to the user. The constructed virtual environment is sent tothe video rendering unit 66.

Specifically, the dynamic object construction unit 64 constructs a modelfor a dynamic object through the six steps shown in FIG. 41. At stepS61, an unprocessed object among objects is set as a processing targetobject. At step S62, if a model of the processing target object isconstructed with CG (YES), the flow proceeds to step S63. Otherwise(NO), the flow proceeds to step S66. At step S63, it is determinedwhether the processing target object whose model is constructed with CGis contained in a region which is constructed with a live-action videoor not. If it is contained (YES), the flow proceeds to step S64.Otherwise (NO), the flow proceeds to step S66. At step S64, a regionwhere the processing target object whose model is constructed with CGhas been pictured is estimated. At step S65, a restoration process isperformed on the region where the processing target object is estimatedto have been pictured. At step S66, if all the objects have beenprocessed (YES), the processing ends. Otherwise (NO), the flow returnsto step S61.

Possible methods for estimating a restoration region at step S64include 1. detecting an object by image processing, and 2. converting asensed object position in field space coordinates into an extrinsiccamera position by utilizing a camera calibrated with respect to thefield space coordinates. These methods will be described below withreference to specific examples.

The method of 1 estimates a restoration region as follows. The followingconsiders a scene where video is synthesized from the batter's boxperspective in baseball and assumes that the model of the ball isconstructed with CG Then, a situation is described where a ball beingactually captured is present in the region of the pitcher, whose modelis constructed with live-action video, and the ball is removed andcomplemented by a video restoration technique. In this case, it ispossible to prepare a ball template and detect the position and size ofan object via template matching in each frame. Alternatively, for anobject whose shape in a camera image is limited to a circle, such as aball, its position and size can be detected by performing circular Houghtransform after edge detection.

The method of 2 estimates a restoration region as follows. In thisapproach, the position of an object sensed in the sensor coordinates isconverted to a camera coordinate system, and the camera coordinates arein turn converted to a screen coordinate system. Assuming transformationmatrices from the sensor coordinates (x, y, z)^(T) to the cameracoordinates (p, q, r)^(T) are A and B, and transformation matrices tothe screen coordinates (s, t)^(T) are C and D, then(p,q,r)^(T) =A(x,y,z)^(T) +B(s,t)^(T) =C(p,q,r)^(T) +DIn this way, an object region to be removed within a video can beestimated.

Estimation of restoration region will be specifically described for thecase of tennis as an example. For video synthesis at the viewpoint at aplayer's position in tennis, the model of the player will be constructedwith a live-action video and the models of a ball and a court will beconstructed with CG, as shown in FIGS. 43 and 44. In the process, a balland a court (a net, lines) caught by the camera that captures the playerare removed. The trajectory of a ball can be easily obtained via thewell-known Hawk-Eye system or the like. The shape of the court ispreviously known from the rules. Accordingly, the three-dimensionalgeometry of the objects whose model is constructed with CG can beobtained. If an extrinsic camera and the world coordinates of the courthave been calibrated, a restoration region can be estimated in a similarway because at which locations the court and the ball will be capturedis known.

For the restoration process at step S65, the image/video restorationtechnique described in Reference Literature 6 below is applicable, forexample.

-   Reference Literature 6: Mariko Isogawa, Dan Mikami, and Akira    Kojima, “Reduction and Synthesis of Feature Values for High Quality    of Experience Image Completion”, IEICE technical report, vol. 114,    no. 239, MVE2014-37, pp. 37-42, October 2014

The viewpoint position/direction acquisition unit 65 obtains virtualviewpoint position and viewpoint direction in the video to be presentedto the user. The position of the virtual viewpoint can be arbitrarilyset in the range established at step 3 by the model construction methoddecision unit 60. The viewpoint position/direction acquisition unit 65obtains virtual viewpoint position and viewpoint direction in the videoto be presented to the user, which have been set and input from outside,and sends them to the video rendering unit 66.

The video rendering unit 66 renders a video of a virtual environment tobe presented to the user using the virtual environment constructed bysynthesis of the environment model and the model of the dynamic object,the virtual environment synthesized by the dynamic object constructionunit 64, and the position and direction of the virtual viewpointobtained by the viewpoint position/direction acquisition unit 65. Therendered video is sent to the video presentation unit 67.

The video presentation unit 67 presents the video rendered by the videorendering unit 66 to the user. The video presentation unit 67 may be aperipheral device connected with the virtual environment constructionapparatus via any of various interfaces, and may employ a common liquidcrystal display, a projector, a head mounted display (HMD), or the like.

The following describes a specific example where a video of a virtualenvironment is constructed from the perspective of the batter's box inbaseball. In this case, the environment model is a stadium and dynamicobjects are assumed to be a pitcher and a ball. A stadium can besubdivided into a batter's box, a home base, a foul line, a stand, andthe like in the order of closeness to the batter. For each of theseobjects, a model construction method is decided by performing the sevensteps described for the model construction method decision unit 60. Thedescription here shows a specific example where a ball thrown by apitcher is the target object.

(Step 1) A ball is thrown by the pitcher from a pitcher plate located at18.44 meters frontward from the batter's box and is caught by a catcherpositioned somewhat behind the home base. That is, given that theapproximate position of the batter in the batter's box is the origin,(0.5, 18.44)-(0.5, −1) is the object presence range of the ball.

(Step 2) Assuming that the camera is present at the side of thebackstop, set the camera position at (1, −20).

(Step 3) Assuming that the virtual viewpoint position is the viewpointof a batter standing in the batter's box, set the virtual viewpointposition at (0, 0).

(Step 4) Based on the information set at steps 1 to 3, determine themaximum θ max of the discrepancy that occurs between the angle when theball is observed by the camera (angle of observation) and the angle whenthe ball is observed from the virtual viewpoint position (angle ofviewing). θ max has positive correlation with the difficulty of modelconstruction using live action. Hereinafter, the discrepancy between theangle of observation and the angle of viewing for ball b will be denotedas θ max(b).

(Step 5) Estimate the difficulty level of sensing for the ball. This isdetermined based on a sensing difficulty level table. Since a ball is arigid body and does not change in appearance when it rotates, it is anobject of low sensing difficulty level. If a system capable of accuratesensing of a ball state, such as the well-known PITCHf/x, is adopted,the sensing difficulty level would be further lower. Hereinafter, ascore of the sensing difficulty level for ball b will be denoted asSE(b).

(Step 6) Estimate the CG drawing difficulty level for the ball. This isdetermined based on a CG drawing difficulty level table. As a ball hasno distortion and is a sphere, creation of a CG model is easy.Hereinafter, a score of the CG drawing difficulty level for ball b willbe denoted as CM(b).

(Step 7) Using the information obtained at steps 4 to 6, check thedetermination formula below. If the determination formula holds, themodel is constructed with a live-action video; if the determinationformula does not hold, the model is constructed with CGSE(b)*CM(b)/θ max(b)≥th

As another example, a specific example where a pitcher is the processingtarget object is described.

(Step 1) During a pitch, a pitcher makes as small movement as movingforward just a step. Thus, (0.5, 18.44)-(0.5, 17.44) is set as theobject presence range of the pitcher.

(Step 2) Assume that the camera position is the same as in the ballexample. That is, it is set at (1, −20). However, it is possible toprepare an observation camera on a per-object basis.

(Step 3) Assume that the virtual viewpoint position is the same as inthe case of the ball. That is, it is set at (0, 0).

(Step 4) Set the discrepancy θ max(p) between the angle of observationand the angle of viewing for pitcher p. As can be seen from FIGS. 42(A)and (B), θ max(p) in the case of pitcher p is a smaller value than θmax(b) in the case of ball b.

(Step 5) In the case of a pitcher (that is, a human), sensing isdifficult because it is an articulated object. Hereinafter, a score ofthe sensing difficulty level for pitcher p will be denoted as SE(p).

(Step 6) In the case of a pitcher, creation of a realistic CG model isvery expensive due to the non-rigidity and complicated deformation ofthe pitcher's uniform. Hereinafter, a score of the CG drawing difficultylevel for pitcher p will be denoted as CM(p).

(Step 7) Using the information obtained at steps 4 to 6, check thedetermination formula below. If the determination formula holds, themodel is constructed with a live-action video; if the determinationformula does not hold, the model is constructed with CGSE(p)*CM(p)/θ max(p)≥th

In this way, whether to construct a model with CG or with a live-actionvideo is determined for each object. Since a model construction methodoptimal for each individual object can be adopted, a realistic virtualenvironment can be constructed.

Specific examples for other sports are briefly described. In theforegoing example of tennis, models of players and a spectator stand areconstructed with live-action video and models of a ball and a court areconstructed with CG The trajectory of a ball can be obtained via thewell-known Hawk-Eye system. A camera for capturing the player may beinstalled outside the court. In the example of soccer, a model of aspectator stand is constructed with live-action video and a model of aground is constructed with CG A player can be either live action or CGdepending on the situation. The position of a player can be obtained viathe well-known TRACAB system and the like.

The virtual environment construction technique in the ninth embodimentconstructs a model by a method optimal for each individual object, thusimproving the reality of a virtual environment constructed by synthesisof objects created with CG and objects captured as live action.

Tenth Embodiment

When a photograph or moving image is taken, an unwanted item could bepictured over an object of interest. As this can significantly degradethe perceived quality of viewing of the captured photograph or movingimage, there is an extremely high demand for a technique for removingsuch an unwanted pictured item by image processing without causingvisual inconsistency. Hereinafter, a region of an image which should beremoved, such as an unwanted pictured item, and a region that cannot beobserved due to occlusion or the like and should be complemented will bereferred to as “complementation target region”. Also, a process whichreceives an image having a complementation target region given as a maskas input and outputs an image having the complementation target regioncomplemented without visual inconsistency with respect to a regionoutside the complementation target region will be referred to as“complementation process”.

A mask indicating the position of a complementation target region isgiven manually or via an existing approach (for example, ReferenceLiterature 7) regardless of whether a still image or a moving image isconcerned. A mask is information indicating whether a region is subjectto processing or not during image processing. For example, it can be amask that indicates a portion to which processing should be applied andthe other portion with binary values separately from an input image, asshown in FIG. 45(1), or a mask that explicitly indicates a region to beprocessed by overlaying a color not used in the image and easilydiscernible on the input image so that processing will not be applied toregions other than the region indicated by the color, as shown in FIG.45(2).

-   Reference Literature 7: Bai, X., Wang, J., Simons, D., Sapiro, G,    “Video snapcut: robust video object cutout using localized    classifiers,” ACM Transactions on Graphics (TOG), vol. 28, Issue 3,    August 2009

Approaches to implement a complementation process on an image and videoinclude a method that searches for regions amenable to restoration in animage in units of patch and sequentially performs complementation basedon patches (for example, Reference Literature 8), and a method thatexamines how much patch-wise translation of an image will find a similarregion and performs complementation based on the resulting information(for example, Reference Literature 9). For a video, a method thatperforms complementation in units of three-dimensional patch taking intoaccount not only the same image but chronological direction (forexample, Reference Literature 10) is used, for example.

-   Reference Literature 8: A. Criminisi, P. Perez, and K. Toyama,    “Region filling and object removal by exemplar-based inpainting,”    IEEE Transactions on Image Processing, vol. 13, no. 9, pp.    1200-1212, September 2004.-   Reference Literature 9: Kaiming He, and Jian Sun, “Image Completion    Approaches Using the Statistics of Similar Patches”, IEEE    Transactions on pattern analysis and machine intelligence, vol. 36,    no. 12, pp. 2423-2435, 2014.-   Reference Literature 10: Alasdair Newson, Andres Almansa, Matthieu    Fradet, Yann Gousseau, Patrick Perez, “Video Inpainting of Complex    Scenes,” SIAM Journal of Imaging Science 2014 7:4, 1993-2019

In a video complementation process for removing an unwanted itempictured in a video and complementing it without sense of inconsistency,if the video is under a fixed-camera condition throughout and the regionto be complemented is a background region, complementation at high speedand with stable image quality is enabled by complementation using pixelvalues from other frames in the same video that correspond to the pixelpositions of the complementation target region. Such a process isdescribed as “paste synthesis”. When a region to be complemented isadjacent to another object (for example, a person) within the frame,however, the above method cannot complement it well because a loss ofthe object occurs. Thus, conventional practices have been adoption of amethod that searches for regions amenable to complementation per framein units of two-dimensional patch, including the vertical and horizontalaxes of an image, and performs complementation, like ReferenceLiteratures 8 and 9, or a method that performs complementation in unitsof three-dimensional patch also taking into account the chronologicaldirection like Reference Literature 10, for example. These methods aredescribed as “completion process” or “patch-search-based completionprocess”.

The conventional complementation approaches however requires an enormouscalculation time for patch search. Thus, for a practical purpose, a longcomplementation time needs to be accepted, or acceleration needs to beattempted such as by the user manually inputting a complementationapproaches or frames to be complemented. This leads to a problem such asoccurrence of a lengthy latency or significant reduction of usabilitydue to manual input by the user.

An object of the tenth embodiment is to provide a video presentationtechnique capable of efficiently complementing a video containing aregion that needs complementation due to an unwanted pictured item orthe like.

To accomplish the object, the video presentation apparatus according toa first aspect of the tenth embodiment includes: a video input unit thatobtains as input a video sequence composed of a plurality of frames andmask information specifying a complementation target region in the videosequence; a complementation method determination unit that separates aframe into a foreground region and a background region based on binaryimages representing differences between the plurality of frames includedin the video sequence, and determines either one of patch-search-basedcompletion and paste synthesis as a complementation method for thecomplementation target region based on a number of pixels belonging tothe foreground region and located within a given distance from aperiphery of the complementation target region; and a videocomplementation unit that complements the complementation target regionin accordance with the complementation method.

The video presentation apparatus according to a second aspect of thetenth embodiment includes: a video input unit that obtains as input avideo sequence composed of a plurality of frames and mask informationspecifying a complementation target region in the video sequence; acomplementation method determination unit that determines either one ofpatch-search-based completion and paste synthesis as a complementationmethod for the complementation target region based on a differencebetween an average color of pixels located within the complementationtarget region and an average color of pixels located within a givendistance from a periphery of the complementation target region; and avideo complementation unit that complements the complementation targetregion in accordance with the complementation method.

The video presentation apparatus according to a third aspect of thetenth embodiment includes: a video input unit that obtains as input avideo sequence composed of a plurality of frames and mask informationspecifying a complementation target region in the video sequence; acomplementation method determination unit that segments each frame inthe video sequence to separate the frame into a foreground segmenthaving a predefined feature and a background segment, and determineseither one of patch-search-based completion and paste synthesis as acomplementation method for the complementation target region based on anumber of pixels belonging to the foreground segment and located withina given distance from a periphery of the complementation target region;and a video complementation unit that complements the complementationtarget region in accordance with the complementation method.

As a way to accomplish the object, the tenth embodiment makes use of thecharacteristics of a fixed camera video of facilitating fast and goodresults of complementation via paste synthesis process, which pastespixels located at corresponding positions in preceding or subsequentframes. That is, if the complementation target region does not overlapanother object (for example, a person) in the frame and pixel values atcorresponding positions in neighboring frames can be used withoutmodification, complementation is performed by pasting pixel values fromanother frame corresponding to the pixel positions that requirecomplementation. On the other hand, if the complementation target regionoverlaps another object in the frame and paste synthesis process usingother frames is difficult, a patch-search-based completion process isperformed. By thus automatically determining a suitable complementationmethod depending on the characteristics of the complementation targetregion, fast, automated, and efficient complementation of video isperformed.

A video presentation apparatus 70 in the tenth embodiment includes avideo input unit 71, a complementation method determination unit 72, avideo complementation unit 73, and a video output unit 74 as shown inFIG. 46. By the video presentation apparatus performing the processes atsteps shown in FIG. 47, the video presentation method in the tenthembodiment is implemented.

The video presentation apparatus is a special device configured byloading of a special program into a known or dedicated computer having acentral processing unit (CPU), main memory (random access memory orRAM), and the like, for example. The video presentation apparatusexecutes various kinds of processing under control of the centralprocessing unit, for example. Data input to the video presentationapparatus and/or data resulting from various kinds of processing arestored in the main memory, for example, and data stored in the mainmemory is read as required to be utilized for other processing. Also, atleast part of the processing components of the video presentationapparatus may be formed of hardware such as an integrated circuit.

Referring to FIG. 47, the processing procedure of the video presentationmethod in the tenth embodiment will be described.

At step S71, the video input unit 71 receives as input a video sequenceV_(orig) composed of multiple frames and mask information D designatinga complementation target region in the video sequence V_(orig). Thevideo sequence V_(orig) and mask information D both havethree-dimensional information on x (information on the x-axis in theframes), y (information on the y-axis in the frames), and t (time axisinformation), which are denoted as V_(orig)(x, y, t), or as V_(orig)(t)when designating only the time axis information. The mask information Dmay be either represented by a set of the positions of the pixelsdesignated as the complementation target {(d_(x1), d_(y1), d_(t1)),(d_(x2), d_(y2), d_(t2)), . . . , (d_(xn), d_(yn), d_(tn))}, or may bemaintained as a binary moving image which indicates a lost region with 1and other region with 0 in a video sequence of the same size as thevideo sequence V_(orig). The video sequence V_(orig) and maskinformation D are sent to the complementation method determination unit72.

At step S72, the complementation method determination unit 72 receivesthe video sequence V_(orig) and mask information D from the video inputunit 71, and decides complementation method P(t) for complementingV_(orig)(t) and reference region R(t) for use in complementation in eachframe t forming the video sequence V_(orig) (1<t<n, where n is the totalnumber of frames in the video sequence V_(orig)). The complementationmethod P(t) represents the complementation method for frame t,indicating either of patch-search-based completion process or pastesynthesis process with 0 or 1, for example. The reference region R(t) isrepresented as R(t)=t′, where t′ is a reference frame vector for framet. The reference frame vector t′ is a scalar vector with one or moreelements, having the frame ID of the reference frame.

Specific methods for deciding the reference frame includes the followingones, for example. In this embodiment, however, any approach that candecide the reference frame may be used without being limited to thefollowing methods.

A first method for deciding the reference frame is one that decidesbased on likeliness of being foreground. This method determines whetheror not a region to be complemented (a complementation target region) offrame t that should be complemented is adjacent to an object which islikely to be foreground, such as a person, in the frame. If the regionis adjacent to such an object, completion process is performed using theinside of the frame as the reference region, and otherwise pastesynthesis process is performed using another frame in which the pixelpositions of the complementation target region are not adjacent to aforeground object.

The reason for determination based on the likeliness of being foregroundwill be described. If the complementation target region is adjacent toan object which is likely to be foreground in the frame, such as aperson, synthesis of pixels at the corresponding positions from anotherframe via a paste synthesis process results in part of the object, suchas a person, being synthesized with background pixels and lost. Incontrast, the patch-search-based completion process finds a regionsuitable for filling in the loss from other regions in the image andperforms a complementation process based on the resulting information,so that a complementation process with lower visual inconsistency islikely to be performed. Thus, determination based on whether or not thecomplementation target region is adjacent to a region which is likely tobe foreground is effective.

First, it is determined whether the complementation target region of thecomplementation target frame t is adjacent to another object in theframe or not. As this determination requires knowledge of the pixelpositions of a region likely to be foreground in the frame, thebackground and the foreground are separated in some way and a foregroundimage S is generated. Although the approach to foreground-backgroundseparation is not specifically limited in this embodiment, a separationprocess can be performed in the following manner, for example.

First, k key frames F in the video sequence V_(orig) are prepared. A“key frame” refers to a frame in a video sequence that is to be used asa reference in execution of the foreground-background separationprocess. While k may be set to any number as long as it satisfies 0<k<n(where n is the total number of frames in the video sequence V_(orig)),for a practical purpose, a number equivalent to about 10% of the totalnumber of frames in the video sequence V_(orig) may be set. The methodfor obtaining key frame F may be determined depending on theapplication, such as random acquisition or acquisition at constantintervals, for example. Then, differential images between thecomplementation target frame t and all of the key frames constitutingthe key frame F are determined and binarized. By this processing, theforeground and the background can be represented as binary values 1 and0 (which is 0 and which is 1 is arbitrary). The total number of thebinary images is also k, the same as the total number of key frames.Then, only those pixels that indicate the foreground in all of the kbinary images are set as the foreground (specifically, the logicalproducts (AND) of the k binary images are determined), and a foregroundimage S is generated.

Once the foreground image S has been generated, the number of pixelsindicating the foreground on the foreground image S and located within agiven distance d from the complementation target region of thecomplementation target frame t is counted, and the total number of themis set as C. If C is smaller than a certain threshold C_(th), it isdetermined that no other object is present in the vicinity of thecomplementation target region, and a completion process is applied usingthe inside of the frame as the reference region with R(t)=t. Otherwise,a reference frame is decided from the frames in the video sequenceV_(orig) and paste synthesis process is performed using the frame as thereference region. Although the distance d may be set to any value equalto or greater than 0 and smaller than the vertical and horizontalresolutions of the image, it may be set to a relatively small value,such as 0<=d<5 [pixel], because it is intended to check for the presenceor absence of an adjacent foreground. For strict checking of adjacencyor non-adjacency, it is set at d=0. While the threshold C_(th) may beset to any value from 0 to 255 inclusive, it may be set to about 50 to150 for a practical purpose. Although the method for deciding thereference frame from the video sequence V_(orig) is not specificallylimited herein, the following methods are possible, for example.

A frame (denoted as t′) close to the complementation target frame t onthe chronological axis is searched in sequence (the search may starteither forward or backward in time), and the foreground-backgroundseparation process described above is performed on the frame t′ to besearched per frame, obtaining a foreground image S′. Then, the number ofpixels indicating the foreground on the foreground image S′ and locatedwithin a given distance d from the complementation target region of thecomplementation target frame t is counted, and the total number of themis set as C. If C is smaller than a certain threshold C_(th), it isdetermined that no other object is present in the vicinity of thecomplementation target region, and completion process is performed usingthe frame t′ as the reference region with R(t)=t′. Otherwise, search iscontinued until frame t′ satisfying the foregoing conditions is found.

A second method for deciding the reference frame is one that is based ondifference in the amount of color feature from surroundings. Inprinciple, this method is similar to the first method for deciding thereference frame, but it decides the reference frame and complementationmethod as described below based only on the amount of color feature.

First, it is checked whether an object to be restored positionallyoverlaps another object present in the frame or not based on the amountof color feature.

An average color of the video sequence V_(orig)(t) at pixel positionscorresponding to the inside of the complementation target region R(t) ofa certain frame t is denoted as U_(in). Also, an average color ofneighborhood pixels that are located within a given distance d from thecomplementation target region R(t) is denoted as U_(out). The distance dmay be set as in the above-described method. U_(in) and U_(out) aredetermined as in the formulae below.

${{U_{in}(t)} = \frac{\overset{\;}{\sum_{{({x,y})} \in \Omega}}{u( {x,y,t} )}}{\sum_{{({x,y})} \in \Omega}1}},{{U_{out}(t)} = \frac{\sum_{{({x,y})} \in {\overset{\_}{\Omega}\bigcap\Theta}}{u( {x,y,t} )}}{\sum_{{({x,y})} \in {\overset{\_}{\Omega}\bigcap\Theta}}1}}$

Here, Ω represents a region of the reference region R(t) that isindicated by mask information D, and Θ represents a region of thereference region R(t) that is located within the given distance d fromthe region indicated by mask information D. u(x, y, t) represents thecolor information (for example, RGB) of V_(orig)(x, y, t).

If the difference U_(diff) between the average colors U_(in) and U_(out)thus determined is smaller than a predefined threshold Th, the referenceregion is set only in the current frame and a completion process isperformed using the inside of the frame as the reference region withR(t)=t. Otherwise, among frames t′ that output U_(out) which makesU_(diff) smaller than threshold Th, a frame closest to the current framet on the chronological axis is selected, and a paste synthesis processis performed using frame t′ as the reference region with R(t)=t′.Although Th may be set to any value from 0 to 255 inclusive, it may beset to about 50 to 150 for a practical purpose. If there are multipleframes t′, only one of them may be selected by random decision, forexample, or multiple frames may be kept as reference regions.

A third method for deciding the reference frame is one that employssegmentation. A known approach to group pixels in an image or video is asegmentation approach, such as Reference Literature 11. Segmentation isa technique to group regions that are similar based on similar colors orstructures into one unitary region with an image as input. Using such anapproach, a segment occupying a large number of pixels in an image canbe identified, allowing the in-image positions of background pixels inframe t to be known. For example, a tag (for example, mound, player,fence, or the like) is first manually assigned by the user to eachsegment in the first frame of a sequence, and segments classified intothe same tags as those tags are checked in the remaining frames, therebyknowing whether a segment of interest is the background or theforeground.

-   Reference Literature 11: Chen, L. Cao, Y. Wang, J. Liu, and X. Tang,    “Image Segmentation by MAP-ML Estimations,” IEEE Transactions on    Image Processing (TIP), vol. 19, no. 9, pp. 2254-2264, 2010.

Utilizing such segmentation, when neighborhood pixels located within thegiven distance d from the complementation target region R(t) of acertain frame t is found to be background, it is determined thatcomplementation only from in-frame information would be easy, and acompletion process is performed using the inside of the frame as thereference region with R(t)=t. Otherwise, among frames t′ in which pixelsat pixel positions corresponding to the complementation target regionR(t) of another frame are background, the frame closest to the currentframe t on the chronological axis is selected, and paste synthesisprocess is applied using frame t′ as the reference region with R(t)=t′.The distance d may be set as in the method described above. If there aremultiple frames t′, only one of them may be selected by random decision,for example, or multiple frames may be kept as reference regions.

At step S73, if the restoration method P received from thecomplementation method determination unit 72 indicatespatch-search-based completion process, the video complementation unit 73receives video sequence V_(orig), mask information D, and referenceregion R from the complementation method determination unit 72, andcomplements the complementation target region in the video sequenceV_(orig) indicated by the mask information D using the reference regionR via a patch-search-based completion process, and generates acomplemented video sequence V_(out). The complemented video sequenceV_(out) is sent to the video output unit 74.

At step S74, if the restoration method P received from thecomplementation method determination unit 72 indicates paste synthesisprocess, the video complementation unit 73 receives the video sequenceV_(orig), mask information D, and reference region R from thecomplementation method determination unit 72, and complements thecomplementation target region in the video sequence V_(orig) indicatedby the mask information D using the reference region R via pastesynthesis process, and generates a complemented video sequence V_(out).The complemented video sequence V_(out) is sent to the video output unit74.

At step S75, the video output unit 74 receives the complemented videosequence V_(out) from the video complementation unit 73 and outputs itthrough an extrinsic video output means. The video output means may be ahead mounted display, a liquid crystal display, a projector, and thelike connected to a video output terminal of the video presentationapparatus, for example.

[Experimental Results with the Tenth Embodiment]

With reference to the experimental results concerning actual calculationtime shown in FIG. 48, improvement in calculation time and image qualityin particular compared to complementation solely by a conventionaltechnique (in-frame completion process or paste synthesis process) isdescribed. The results shown in (1) to (4) of FIG. 48 are as follows.(1) (He+2014) is an experimental result based on the in-frame completionprocess described in Reference Literature 9. (2) (Paste synthesis) is anexperimental result with paste synthesis process. (3) (Newson+2014) isan experimental result with the moving image completion process based onthree-dimensional patch described in Reference Literature 10. (4) (Thepresent technique) is an experimental result with the video presentationapparatus of the tenth embodiment. The results shown in (A) and (B) ofFIG. 48 are experimental results for the following video sequences,respectively. (A) A video with its sequence including a frame in which aball as the restoration target region is adjacent to a pitcher as aforeground region, thus making paste synthesis process difficult,whereas sense of inconsistency is less likely to occur in the result ofapplying in-frame completion because the background is uniform. (B) Avideo with no frame in which a ball as the restoration target region isadjacent to or overlaps a pitcher as a foreground region in a sequence,thus making paste synthesis process relatively easy, whereas in-framecompletion is difficult because the background contains complicatedtexture such as a fence.

Image quality obtained when the calculation times in FIG. 48(A) werecomputed in experiments is described below. (A) is an experimentalresult using a scene that cannot be complemented well by paste synthesisprocess in the frame of interest because it includes a frame in which aball as the complementation target region is adjacent to a person(pitcher), but on the other hand causes low sense of inconsistency evenwith in-frame completion because the background is uniform. When thebackground does not contain texture complicated by soil of a mound orthe like, sense of inconsistency upon application of in-frame completionis low; thus, the in-frame completion process of (1) is effective forthis scene. In contrast, with the paste synthesis process of (2), if theremoval target region is adjacent to a foreground, pasting of pixelsfrom another frame results in part of the pitcher's body beingcomplemented with pixels of a mound soil region, leading to significantdegradation of image quality. The moving image completion process of (3)is also effective, but it incurs an enormous calculation time (see FIG.48). The present technique of (4) determines which one of (1) and (2) isan appropriate complementation approach per frame; the in-framecompletion process of (1) was determined to be appropriate for frameswhose image quality significantly degraded with the paste synthesisprocess of (2), whereas the faster process, namely (2), was selected forthe other frames. Consequently, the image quality was significantlyimproved relative to (2).

Image quality obtained when the calculation times in FIG. 48(B) werecomputed in experiments is described below. (B) is an experimentalresult using a scene that causes low sense of inconsistency even withcomplementation using paste synthesis process because a ball as thecomplementation target region is not adjacent to a person, whereas thebackground contains complicated texture structures and in-framecompletion is likely to fail. When the background has a complicatedtexture structure, such as a fence, the in-frame completion of (1) islikely to fail in complementation of the background texture, causing aframe complemented with a loss of a linear structure of the fence.Consequently, temporal consistency is not maintained, which can causesignificant sense of inconsistency when it is viewed as a moving imagesequence. In contrast, with the paste synthesis process of (2),synthesis with low sense of inconsistency was possible because it canuse a correct texture structure present in another frame. As with theexample (A), the moving image completion process of (3) is alsoeffective, but it incurs an enormous calculation time (see FIG. 48). Thepresent technique of (4) performs complementation using the method of(2) when the ball as the complementation target region is not adjacentto the foreground (the pitcher), so that the approach (2), whichperforms complementation from another frame, was determined to beappropriate also for a frame that was complemented with a loss of alinear structure of the fence with the approach of (1). Consequently,the image quality was significantly improved relative to (1).

In the examples of FIGS. 48 (A) and (B), either the paste synthesisprocess or the completion process failed, respectively, resulting incomplementation with sense of inconsistency. By using either of the twoapproaches depending on the frame via automated determination, thepresent technique is capable of automatically performing successfulcomplementation of even a scene which was difficult to complementpreviously.

FIG. 48 shows the results of comparing the execution times for thescenes shown in (A) and (B), respectively. The paste synthesis processof (2) requires the smallest execution time in all the cases, but can beinsufficient in terms of image quality as mentioned above. In contrast,the present technique shown in (4) improves the image quality whilehaving the next smallest calculation time to (2) (an execution time of31.1% of (1) in (A), and an execution time of 2.5% of (1) in (B)).Therefore, the present technique is considered to be effective in thatit can shorten the calculation time while improving the image quality.

With the configuration described above, the tenth embodiment performscomplementation by a patch-search-based completion process if aforeground object is present in the vicinity of the complementationtarget region and by a paste synthesis process if there is no foregroundobject in the vicinity of the complementation target region. It can thusefficiently complement a video containing a region that requirescomplementation due to an unwanted pictured item or the like.

Eleventh Embodiment

In these years, cameras capable of capturing a 360° panoramic image(hereinafter referred to as “omnidirectional cameras”) have beenincreasingly popular. A panoramic image (hereinafter referred to as“omnidirectional image”) captured by an omnidirectional camera can becaptured by installing an omnidirectional camera at a desired viewpointposition. However, since it hinders players in play, an omnidirectionalcamera cannot be installed in a sports court such as a soccer court or abasket court. Thus, it is not possible to capture an omnidirectionalimage during play at a desired viewpoint position in a sports court.

Accordingly, one proposed technique sets a virtual viewpoint, which isan imaginary viewpoint, at a location where an omnidirectional cameracannot be installed and obtains an omnidirectional image looking likeone captured by an omnidirectional camera at the virtual viewpoint bysynthesizing images captured by multiple cameras installed outside thecourt (see Reference Literature 5, for instance). In the followingdescription, an omnidirectional image at a virtual viewpoint isdescribed as a virtual omnidirectional image.

A specific example of a system that obtains a virtual omnidirectionalimage by synthesis of images captured by multiple cameras is described.

FIG. 61 is a diagram showing a system for obtaining a virtualomnidirectional image with a conventional system. As shown in FIG. 61,an image processing system 900 includes an omnidirectional camera 92,multiple cameras 93-1, 93-2, 93-3, . . . , 93-N (hereinafter referred toas “camera group 93”) (N being an integer equal to or greater than 4),an image processing device 94, and a display device 95. In a case wherea virtual viewpoint 91 is set within a sports court 90, the imageprocessing system 900 obtains a virtual omnidirectional image at thevirtual viewpoint 91 by synthesis of images captured by the camera group93 installed outside the sports court 90.

The omnidirectional camera 92 is a camera for capturing omnidirectionalimages. The omnidirectional camera 92 is installed at the position ofthe virtual viewpoint 91 in the sports court 90 at a timing prior toplay. The omnidirectional camera 92 captures an image to be a backgroundin a virtual omnidirectional image from the position of the virtualviewpoint 91 (hereinafter referred to as “background image”). Thebackground image captured by the omnidirectional camera 92 is input toand accumulated in the image processing device 94. In this manner, theimage processing device 94 accumulates background images beforehand.

Around the sports court 90, the camera group 93 is installed. Thecameras 93-1, 93-2, 93-3, . . . , 93-N of the camera group 93 areinstalled around the sports court 90 such that each has an angle of viewincluding the virtual viewpoint 91. The camera group 93 captures aregion including the virtual viewpoint 91. The image processing device94 applies image processing to images captured by the cameras 93-1,93-2, 93-3, . . . , 93-N of the camera group 93 and synthesizes theimages after the image processing with a background image to generate avirtual omnidirectional image. The display device 95 is an image displaydevice, such as a liquid crystal display, an organic electroluminescence (EL) display, or a cathode ray tube (CRT) display. Thedisplay device 95 displays the virtual omnidirectional image generatedby the image processing device 94.

Next, a specific example of image processing in the image processingsystem 900 is described with FIG. 62.

FIG. 62 is a diagram for describing a flow of image processing in theimage processing system 900. FIG. 62(A) is a diagram showing a specificexample of a background image 920. In the background image 920, subjectsin all directions (360 degrees) about the virtual viewpoint 91 arecaptured. Since the background image 920 is an image captured when thereare no people in the sports court 90, no people are captured in thesports court 90.

FIG. 62(B) is a diagram showing images captured by cameras 93-1, 93-2,and 93-3. In FIG. 62(B), from the left, an image 921 captured by thecamera 93-1, an image 922 captured by the camera 93-2, and an image 923captured by the camera 93-3 are shown. The image processing device 94extracts regions 9211, 9221, 9231 including the virtual viewpoint 91from the images 921 to 923, respectively. The image processing device 94performs image processing on the images of the extracted regions 9211,9221, 9231, thereby generating partial images 9211 a, 9221 a, 9231 a,which can be synthesized with the background image 920.

The image processing device 94 synthesizes the partial images 9211 a,9221 a, 9231 a with the background image 920 to thereby generate avirtual omnidirectional image 924. FIG. 62(C) is a diagram showing anexample of a virtual omnidirectional image 924 generated by the imageprocessing device 94. As shown in FIG. 62(C), in predetermined regionsof the virtual omnidirectional image 924, the partial images 9211 a,9221 a, 9231 a have been synthesized. Consequently, an image withsubjects (for example, people) captured on the sports court 90 isgenerated as the virtual omnidirectional image 924. In the conventionalimage processing system 900, the optical centers of the camera group 93used for synthesis and the optical center of the omnidirectional camera92 imagined at the virtual viewpoint 91 are different from each other.Thus, a synthesized virtual omnidirectional image 924 contains ageometrically incorrect image. To prevent this, the image processingdevice 94 needs to perform image processing on the partial images 9211a, 9221 a, 9231 a so as to maintain consistency at a point in depth,which indicates the distance from the virtual viewpoint 91, andsynthesize them with the background image 920.

However, when a partial image of a subject (for example, a person) thatis not present at a depth at which consistency can be maintained butpresent at another depth is synthesized with the background image 920,the consistency of depth cannot be maintained through image processing.Such a subject lacking depth consistency causes phenomena such as itsimage becoming a multi-image or disappearing in the virtualomnidirectional image 924. Thus, when the depth of a subject is notknown, there is the problem of appropriate synthesis being impossible.This problem is common to all cases of synthesizing images captured bymultiple image capturing devices.

In view of the situation, an object of the eleventh embodiment is toprovide a technique capable of deciding an optimal depth for an imagecaptured by each of multiple image capturing devices.

An aspect of the eleventh embodiment is an optimal depth decisionapparatus including a decision unit that, using a plurality of inputimages respectively captured by at least two image capturing deviceinstalled around a region including a predetermined position such thatthe region including the predetermined position will be an imagecapturing range, and assuming that the predetermined position is avirtual viewpoint which is an imaginary viewpoint, generates syntheticimages with a plurality of different depths representing distances fromthe virtual viewpoint, computes a contrast from each of multiplesynthetic images generated, and decides a depth of a synthetic imagewith a highest contrast among the multiple synthetic images as anoptimal depth for each input image based on the computed contrasts.

The eleventh embodiment will be described below with reference todrawings.

FIG. 49 is a diagram showing a system configuration of an imageprocessing system 800 in the eleventh embodiment.

The image processing system 800 includes an omnidirectional camera 92,multiple cameras 93-1 to 93-M (M being an integer equal to or greaterthan 2), and an image processing device 80. In the followingdescription, the cameras 93-1 to 93-M will be described as camera 93when they are not specifically distinguished.

The omnidirectional camera 92 is installed at the position of a virtualviewpoint 82 in an image-capturing target region 81. The image-capturingtarget region 81 is a sports court such as a soccer court or a basketcourt, for example. The virtual viewpoint 82 is a viewpoint virtuallyset in a predetermined region (the image-capturing target region 81 inthis embodiment). The omnidirectional camera 92 captures anomnidirectional image at the position of the virtual viewpoint 82. Anomnidirectional image in this embodiment includes the entireimage-capturing target region 81 around the virtual viewpoint 82.Processing by the omnidirectional camera 92 is performed before start ofprocessing by the image processing device 80. The omnidirectional camera92 outputs a captured omnidirectional image to the image processingdevice 80 as a background image.

The M cameras 93-1, 93-2, . . . , 93-M are cameras provided outside theimage-capturing target region 81 for capturing images as moving images(video), and they capture regions including the virtual viewpoint 82.Moving images captured by the M cameras 93-1, 93-2, . . . , 93-M arecomposed of multiple-frame images. As shown in FIG. 49, a ray 83-1passing over the position of the virtual viewpoint 82 is input to thecamera 93-1, while a ray 83-2 passing over the position of the virtualviewpoint 82 is input to the camera 93-2. Hereinafter, a ray input tothe camera 93 will be described as actual ray. Although not shown inFIG. 49, the cameras 93 are installed around the image-capturing targetregion 81. That is, the cameras 93 are installed so as to surround theimage-capturing target region 81 such that each has an angle of viewincluding the virtual viewpoint 82. In FIG. 49, M is an integer equal toor greater than 2 and is a greater value as the image-capturing targetregion 81 is larger if a virtual omnidirectional image of similar imagequality is to be obtained. Also, given the image-capturing target region81 of the same size, a greater value of M results in a larger area of asynthetic region (a region where images from the M cameras 93 aresynthesized in a virtual omnidirectional image), or given the syntheticregion of the same size, a greater value of M is required for yieldinghigher image quality of a virtual omnidirectional image, which in turnimproves the image quality of the synthetic region.

The image processing device 80 obtains input images from moving imagesrespectively captured by the M cameras 93-1, 93-2, . . . , 93-Mbeforehand. The captured moving images are each composed ofmultiple-frame images, and the image processing device 80 in thisembodiment obtains as an input image an image of a frame to beprocessed. The image processing device 80 generates a virtualomnidirectional image based on an omnidirectional image captured by theomnidirectional camera 92 and on input images obtained respectively frommoving images captured by the M cameras 93-1, 93-2, . . . , 93-Mrespectively. Specifically, the image processing device 80 decides theoptimal depth from an input image, extracts a region from the inputimage based on the depth decided, and overlays the extracted region onthe omnidirectional image, thereby generating a virtual omnidirectionalimage.

The eleventh embodiment is described for the case where two neighboringcameras 93 (cameras 93-1 and 93-2) are provided in the image processingsystem 800 as an example. In the following description, the set of theneighboring cameras 93 (for example, the set of cameras 93-1 and 93-2)will be described as camera pair.

The image processing device 80 has a central processing unit (CPU),memory, an auxiliary storage device, and the like connected by a bus,and executes an image processing program. By executing the imageprocessing program, the image processing device 80 functions as a deviceincluding an input image storage 801, a synthesis information storage802, a decision unit 803, an optimal depth storage 804, a backgroundimage storage 805, and an image synthesis unit 806. All or some of thefunctions of the image processing device 80 may be implemented withhardware, such as an application specific integrated circuit (ASIC), aprogrammable logic device (PLD), or a field programmable gate array(FPGA). The image processing program may be recorded in acomputer-readable recording medium. A computer-readable recording mediumis a storage device such as a portable medium like a flexible disk,magneto-optical disk, ROM, or CD-ROM, or a hard disk built in a computersystem, for example. The image processing program may also betransmitted and received via a telecommunication line.

The input image storage 801 is configured with a storage device such asa magnetic hard disk device or a semiconductor storage device. The inputimage storage 801 stores input images from each camera 93 inchronological order in association with a camera ID identifying thecamera 93. An input image includes the time of its capturing and imagedata of a moving image.

The synthesis information storage 802 is configured with a storagedevice such as a magnetic hard disk device or a semiconductor storagedevice. The synthesis information storage 802 stores a synthesisinformation table. The synthesis information table is composed ofrecords (hereinafter “synthesis information records”) representinginformation used for overlaying an image on a background image(hereinafter “synthesis information”).

FIG. 50 is a diagram showing a specific example of the synthesisinformation table.

The synthesis information table has multiple synthesis informationrecords. A synthesis information record has the values of camera ID andsynthesis information. The value of camera ID represents identificationinformation for identifying a camera 93. For example, the camera 93identified by camera ID “C₁” in FIG. 50 is camera 93-1, and the camera93 identified by camera ID “C₂” is camera 93-2.

The value of synthesis information represents information used foroverlaying an image generated from an image (an input image) captured bythe camera 93 identified by the camera ID of the same synthesisinformation record on a background image. Specific examples of synthesisinformation include depth, extraction region information, and conversioninformation.

The depth value of a certain synthesis information record represents thedistance of the camera 93 identified by the camera ID from the virtualviewpoint 82. In the example shown in FIG. 50, N levels of depth areregistered in the synthesis information table per camera ID. N is aninteger equal to or greater than 2. Depth 1 to depth N are set betweenthe virtual viewpoint 82 and an edge of the image-capturing targetregion 81. The number of depths being set is preferably a number thatensures the accuracy of optimal depth decision to a certain degree.

The value of extraction region information in a certain synthesisinformation record represents information concerning a region to beextracted from an image (input image) captured by camera 93 identifiedby the camera ID (hereinafter referred to as “extraction region”).Specific examples of extraction region information include upper leftcoordinates, width, and height. The upper left coordinates representscoordinates at the upper left corner of the extraction region. The widthrepresents the width of the extraction region. The height represents theheight of the extraction region. The width and height are set in a rangethat is referenced to the upper left coordinates of the extractionregion and that includes the virtual viewpoint 82. The extraction regionis desirably set as a region such that no gap is formed between imagesfrom neighboring cameras 93 in an image overlaid on a background image.In the following description, an image of a partial region extractedfrom an input image in accordance with extraction region information isdescribed as partial region image.

The value of conversion information in a certain synthesis informationrecord represents information for converting a partial region imageextracted in accordance with the extraction region information to apartial image. A partial image is generated by applying a deformationprocess, such as zooming up, zooming down, and rotation, on a partialregion image in accordance with conversion information in order tooverlay the partial region image on a corresponding region of abackground image without sense of inconsistency. The deformation processis performed by applying affine transformation to the image, forexample. Conversion information in the case of applying affinetransformation to an image is an affine transformation matrix, forexample. While the following shows an example of using affinetransformation as the deformation process on a partial region image, thedeformation process needs not be limited to affine transformation butmay be any kind of processing that performs transformation of an image,such as by zooming up, zooming down, and rotation, in accordance withconversion information. The affine transformation matrix includesinformation indicating a region on which a partial image is overlaid ina background image (hereinafter referred to as “overlay information”).

An affine transformation matrix is derived in advance in the mannershown below and stored in the synthesis information storage 802. Forexample, a chessboard with a grid pattern is placed at each of positionslocated at different distances (depths) (depth 1 to depth N in theexample of FIG. 50) from the virtual viewpoint 82, and an imageincluding the chessboard captured by the omnidirectional camera 92installed at the virtual viewpoint 82 is compared with an imageincluding the chessboard captured by the camera 93. Then, for each gridof the chessboard, an affine transformation matrix is determined thatconverts the images such that the grid of the chessboard in the imagecaptured by the omnidirectional camera 92 and the grid of the chessboardin the image captured by the camera 93 correspond to each other. In thismanner, an affine transformation matrix corresponding to each of depth 1to depth N, at which the chessboard is placed, is determined.

As shown in FIG. 50, in the synthesis information table, N levels ofdepth are registered per camera ID, and conversion information isregistered for each of depths 1 to N. In FIG. 50, the synthesisinformation record registered in the topmost row of the synthesisinformation table has a camera ID value of “C₁”, a depth value of “depth1”, an upper left coordinate value of “(A, B)”, a width value of “C”, aheight value of “D”, and a conversion information value of “A1_(j1)” (jis an integer equal to or greater than 1). That is, it indicates that inthe case of depth 1 for the camera 93-1 identified by camera ID “C₁”,the partial region represented by the upper left coordinates (A, B), thewidth C, and the height D is extracted from an input image, and thedeformation process “A1_(j1)” is applied to the extracted partialregion.

Referring back to FIG. 49, description on the image processing device 80is continued.

The decision unit 803 takes input images of the camera pair stored inthe input image storage 801 and the synthesis information table storedin the synthesis information storage 802 as input. The decision unit 803decides the optimal depth for each input image of each camera 93 basedon the input images of the camera pair and the synthesis informationtable input to it. Here, an optimal depth represents a depth at which amulti-image or disappearance is less visible than at other depths inrelation to a subject captured in an input image.

Next, specific processing by the decision unit 803 will be described.

The decision unit 803 first generates a partial region image of eachinput image by extracting a partial region from the input image based onextraction region information corresponding to one depth (for example,depth 1) in the synthesis information table. The decision unit 803 thenperforms a deformation process based on the affine transformation matrixin conversion information corresponding to the one depth (for example,depth 1) in the synthesis information table on the generated partialregion image of each input image, thereby generating a partial image ofeach input image. The decision unit 803 then uses the generated partialimage of each input image to generate a synthetic image for deciding theoptimal depth for each input image (hereinafter referred to as “depthdecision synthetic image”). For example, the decision unit 803 generatesa depth decision synthetic image based on overlay information includedin conversion information. The decision unit 803 computes a contrast ofan overlapping region of the generated depth decision synthetic image.In this embodiment, a case where contrast is determined as luminancedifference is described by way of example. For determination of contrastas luminance difference, Formula 1 discussed later is used. The decisionunit 803 performs the above process on all of the depths 1 to N. Thedecision unit 803 then decides the depth of the depth decision syntheticimage with the highest contrast among the contrasts computed at all thedepths 1 to N as the optimal depth for each input image of the camerapair. The decision unit 803 decides the optimal depth for each inputimage of each camera 93 from the optimal depth decided for each inputimage of the camera pair. When there is a single camera pair as in thisembodiment, the decision unit 803 may decide the optimal depth for eachinput image of the camera pair as the optimal depth for input image ofeach camera 93. A case with multiple camera pairs is described later.The decision unit 803 stores the decided optimal depth information foreach input image of each camera 93 in the optimal depth storage 804. Thedecision unit 803 performs the above process on the input images of thecamera pair at each time.

The optimal depth storage 804 is configured with a storage device suchas a magnetic hard disk device or a semiconductor storage device. Theoptimal depth storage 804 stores the optimal depth information table.The optimal depth information table is composed of records representinginformation about the optimal depth for each input image of each camera93 (hereinafter referred to as “optimal depth information record”).

FIG. 51 is a diagram showing a specific example of the optimal depthinformation table.

The optimal depth information table has multiple optimal depthinformation records. An optimal depth information record has the valuesof time and optimal depth. The value of time represents the time atwhich the input image was captured. The value of optimal depth in acertain optimal depth information record represents the optimal depthfor the input image of each camera 93 captured at a certain time.

In the example shown in FIG. 51, information on optimal depth at eachtime is registered in the optimal depth information table. In FIG. 51,the optimal depth information record registered in the topmost row ofthe optimal depth information table has a time value of “t”, an optimaldepth value for the input image of camera 93-1 of “d1(t)”, and anoptimal depth value for the input image of camera 93-2 of “d2(t)”. Thatis, it indicates that the optimal depths for the images (input images)captured by cameras 93-1 and 93-2 at time t are “d1(t)” and “d2(t)”respectively.

The background image storage 805 is configured with a storage devicesuch as a magnetic hard disk device or a semiconductor storage device.The background image storage 805 stores an omnidirectional imagecaptured by the omnidirectional camera 92 as a background image.

The image synthesis unit 806 takes as input an input image of eachcamera 93 stored in the input image storage 801, the synthesisinformation table stored in the synthesis information storage 802, theoptimal depth information table stored in the optimal depth storage 804,and a background image stored in the background image storage 805. Theimage synthesis unit 806 generates a virtual omnidirectional image basedon the input image of each camera 93, the synthesis information table,the optimal depth information table, and the background image input toit. Specifically, the image synthesis unit 806 references the optimaldepth information table to obtain information on the optimal depth forthe input image of a certain camera 93 (for example, camera 93-1) at acertain time (for example, time t). The image synthesis unit 806 obtainsextraction region information corresponding to the optimal depth for thecertain camera 93 (for example, camera 93-1) from the synthesisinformation table based on the obtained optimal depth for the inputimage of the camera 93. The image synthesis unit 806 extracts a partialregion from the input image based on the obtained extraction regioninformation to thereby generate a partial region image.

The image synthesis unit 806 obtains conversion informationcorresponding to the optimal depth for the certain camera 93 (forexample, camera 93-1) from the synthesis information table. The imagesynthesis unit 806 performs a deformation process based on the affinetransformation matrix in the obtained conversion information on thegenerated partial region image to thereby generate a partial image ofthe input image. The image synthesis unit 806 performs processing up togeneration of a partial image on the input image of each camera 93 at acertain time. Subsequently, the image synthesis unit 806 overlays thegenerated partial image on the background image based on the overlayinformation included in the affine transformation matrix, therebygenerating a virtual omnidirectional image. More specifically, the imagesynthesis unit 806 generates a virtual omnidirectional image byreplacing the pixel values in a region of the background image ontowhich the partial image is to be overlaid with the pixel values of thepartial image. The image synthesis unit 806 performs processing forgenerating a virtual omnidirectional image on input images at each time,thereby generating a virtual omnidirectional image at each time. Theimage synthesis unit 806 outputs the generated virtual omnidirectionalimage.

In the following description, the entire processing by the imagesynthesis unit 806 described above will be described as image synthesisprocess step.

FIG. 52 is a diagram showing a specific example of contrast computationresults.

In FIG. 52, the vertical axis represents contrast and the horizontalaxis represents depth. A depth value closer to 0 represents a depth at ashorter distance from the virtual viewpoint 82, and a higher depth valuerepresents a depth at a longer distance from the virtual viewpoint 82.In FIG. 52, the contrast at depth d, indicated by a circle 990, ishighest. In this case, the decision unit 803 decides depth d as theoptimal depth for each input image of the camera pair.

FIG. 53 is a flowchart showing a flow of processing by the imageprocessing device 80.

The decision unit 803 reads input images of the camera pair at anidentical time from the input image storage 801 (step S101). Thedecision unit 803 then generates a depth decision synthetic image usingconversion information for one depth based on the input images it readout and the synthesis information table stored in the synthesisinformation storage 802 (step S102). For selection of one depth, anymethod that can select a depth not already processed may be used. Forexample, the decision unit 803 may select depths in sequence startingfrom a depth closer to the virtual viewpoint 82, randomly select depths,or otherwise select depths. The decision unit 803 then computes acontrast of an overlapping region of the generated depth decisionsynthetic image based on Formula 1 below (step S103). Formula 1 is anexample of the way of determining a contrast. In Formula 1, L_(min)represents the minimum luminance value of an overlapping region in animage, and L_(max) represents the maximum luminance value of theoverlapping region in the image.

$\begin{matrix}{{Contrast} = \frac{L_{\max} - L_{\min}}{L_{\max} + L_{\min}}} & ( {{Formula}\mspace{14mu} 1} )\end{matrix}$

Subsequently, the decision unit 803 determines whether the contrastcomputation process has been performed on all the depths or not (stepS104). If the contrast computation process has not been performed on allthe depths (step S104: NO), the decision unit 803 repeatedly executesthe processing at step S102 onward.

In contrast, if the contrast computation process has been performed onall the depths (step S104: YES), the decision unit 803 decides theoptimal depth for each input image of the camera pair based on thecontrasts computed for all the depths (step S105).

In the following description, the process from step S102 to step S105 inFIG. 53 will be described as camera pair depth decision process.

The image processing device 80 configured as described above can decidethe optimal depth for an image captured by each of multiple imagecapturing devices. This effect will be described in detail below.

The image processing device 80 uses input images of the camera pair togenerate depth decision synthetic images for all depths. The imageprocessing device 80 then computes a contrast from each of the depthdecision synthetic images generated for all depths, and selects thedepth decision synthetic image with the highest contrast computed. Whencontrast is low, the image is likely to be blurry. That is, it is likelyto be an image with occurrence of a multi-image or disappearanceassociated with synthesis. Accordingly, the image processing device 80can select an image less likely to have occurrence of a multi-image ordisappearance by selecting the depth decision synthetic image with thehighest contrast. Thus, the optimal depth for an image captured by eachof multiple image capturing devices can be decided.

Modification of the Eleventh Embodiment

The input image storage 801, the synthesis information storage 802, thedecision unit 803, and the optimal depth storage 804 of the imageprocessing device 80 may be configured as an optimal depth decisionapparatus.

Although this embodiment describes a case with a single camera pair, twooptimal depths would be present for each camera 93 when there aremultiple camera pairs. For example, for a certain camera C_(i) (i is aninteger equal to or greater than 2), there are (C_(i−1), C_(i)) pair and(C_(i), C_(i+1)) pair, and an optimal depth is decided for each of thecamera pairs. Thus, when there are multiple camera pairs, the decisionunit 803 decides the optimal depth for camera C_(i) based on optimaldepths decided with the respective pairs (for example, (C_(i−1), C_(i))pair and (C_(i), C_(i+1)) pair). Methods for this include one thatdecides one of the two optimal depths closer to the virtual viewpoint 82as the optimal depth for camera C_(i). By performing this processing onall camera pairs, the decision unit 803 can decide the optimal depth foreach input image of each camera 93 even when there are multiple camerapairs. The decision unit 803 then stores information on the optimaldepth decided for each input image of each camera 93 in the optimaldepth storage 804. Subsequently, the image synthesis unit 806 mayexecute the image synthesis process step, may execute the imagesynthesis process step at the timing of input of an instruction forsynthetic image generation, or may execute the image synthesis processstep at another timing.

In selection of a camera pair, a method that prevents presence of twooptimal depths for one camera 93, such as selecting (C_(i−1), C_(i))pair and (C_(i+1), C_(i+2)) pair, may be adopted.

Twelfth Embodiment

The twelfth embodiment achieves faster processing than the eleventhembodiment. Specifically, the eleventh embodiment performs the contrastcomputation process for all of N depths, whereas in the twelfthembodiment, the image processing device decides the optimal depth foreach input image of a camera pair based on a smaller number of depthsthan in the eleventh embodiment. More specifically, in the twelfthembodiment, the image processing device creates a new depth candidategroup such that the intervals between depths included in the depthcandidate group becomes narrower on each iteration of processing, anddecides the optimal depth from the depths included in the final depthcandidate group at a point when it has been repeated a predeterminednumber of times. Also, the twelfth embodiment will be described for thecase where two cameras 93 (cameras 93-1 and 93-2) are provided in theimage processing system 800 as a camera pair, as in the eleventhembodiment.

FIG. 54 is a schematic block diagram representing a functionalconfiguration of an image processing device 80 a in the twelfthembodiment. The image processing device 80 a has a CPU, memory, and anauxiliary storage device connected by a bus, and executes an imageprocessing program. By executing the image processing program, the imageprocessing device 80 a functions as a device including the input imagestorage 801, the synthesis information storage 802, the decision unit803 a, the optimal depth storage 804, the background image storage 805,and the image synthesis unit 806. All or some of the functions of theimage processing device 80 a may be implemented with hardware, such asan ASIC, a PLD, or a FPGA. The image processing program may be recordedin a computer-readable recording medium. A computer-readable recordingmedium is a storage device such as a portable medium like a flexibledisk, magneto-optical disk, ROM, or CD-ROM, or a hard disk built in acomputer system, for example. The image processing program may also betransmitted and received via a telecommunication line.

The image processing device 80 a differs from the image processingdevice 80 in configuration in that it includes a decision unit 803 ainstead of the decision unit 803. For the remaining configuration, theimage processing device 80 a is similar to the image processing device80. Thus, description on the image processing device 80 a as a whole isomitted and only the decision unit 803 a is described.

The decision unit 803 a takes input images of the camera pair stored inthe input image storage 801 and the synthesis information table storedin the synthesis information storage 802 as input. The decision unit 803a decides the optimal depth for each input image of each camera 93 basedon the input images of the camera pair and the synthesis informationtable input to it.

Next, specific processing by the decision unit 803 a is described.

The decision unit 803 a first selects particular depths (for example, Sdepths) out of N depths. Here, methods for selecting particular depthsinclude one that selects depths at equal intervals (at intervals ofN/S). Hereinafter, such processing for selecting particular depths outof N depths will be described as initial processing. Depths selected inthe initial processing are described as initial depth candidate group.The decision unit 803 a then references the synthesis information tableto generate a depth decision synthetic image for each depth included inthe initial depth candidate group, and computes the contrast of thegenerated depth decision synthetic image. Processing relating togeneration of depth decision synthetic images and computation ofcontrast is similar to the eleventh embodiment. By this processing, thedecision unit 803 a generates a depth decision synthetic image andcomputes a contrast at each depth included in the initial depthcandidate group. The decision unit 803 a then creates a new depthcandidate group including the depth with the highest contrast among thecomputed contrasts. When creating a new depth candidate group, thedecision unit 803 a creates a new depth candidate group from a rangecentered at the depth with the highest contrast. The range of centeringis predefined.

Processing for creating a new depth candidate group including the depthwith the highest contrast will be described below. The description herediscusses processing for creating a new depth candidate group whileshowing an example of how to define a range centered at the depth withthe highest contrast. As an example, assume that there are five depths(N=5; five depths S1, S2, S3, S4, S5 (S1<S2<S3<S4<S5)).

The decision unit 803 a selects a predetermined number of depths betweenthe depth with the highest contrast and depths neighboring the depthwith the highest contrast. For example, if the depth with the highestcontrast is S3, the neighboring depths are S2 and S4. In this manner,the decision unit 803 a sets the range between depths neighboring thedepth with the highest contrast (for example, between S2 and S4) as a“range centered at the depth with the highest contrast”. Then, thedecision unit 803 a selects T (T is an integer equal to or greaterthan 1) depths from the “range centered at the depth with the highestcontrast” (for example, between S2 and S4). For example, T depths may beselected at equal intervals from among depths between the depthsneighboring the depth with the highest contrast (in the range centeredat the depth with the highest contrast) stored in the synthesisinformation table. Subsequently, the decision unit 803 a creates a newdepth candidate group that includes the depth with the highest contrast(for example, S3) and T depths selected from the depths between thedepths neighboring the depth with the highest contrast (for example,between S2 and S4). That is, the decision unit 803 a creates a new depthcandidate group including T+1 depths.

The decision unit 803 a generates a depth decision synthetic image foreach of the depths included in the new depth candidate group created,and computes a contrast of the generated depth decision synthetic image.In doing so, the decision unit 803 a does not have to perform processingon depths for which contrast is already computed. The decision unit 803a performs the above process a predetermined number of times. Then, itdecides the depth with the highest contrast in the depth candidate groupafter the predetermined number of executions as the optimal depth foreach input image of the camera pair. The decision unit 803 a performsthe above process on the input images of the camera pair at each time.

FIG. 55 is a flowchart showing a flow of processing by the imageprocessing device 80 a.

The decision unit 803 a reads input images of the camera pair at anidentical time from the input image storage 801 and inputs them (stepS201). The decision unit 803 a then creates an initial depth candidategroup by selecting S depths out of N depths (step S202). Specifically,the decision unit 803 a creates an initial depth candidate group byselecting a particular number of depths from preset multiple depths. Theprocessing for creating the initial depth candidate group is performedonly in the initial processing. The decision unit 803 a generates adepth decision synthetic image using the conversion information for oneof the depths included in the depth candidate group based on the inputimage it read out and the synthesis information table stored in thesynthesis information storage 802 (step S203). The decision unit 803 acomputes the contrast of an overlapping region of the generated depthdecision synthetic image based on Formula 1 above (step S204).Subsequently, the decision unit 803 a determines whether the contrastcomputation process has been performed on all the depths included in thedepth candidate group or not (step S205). If the contrast computationprocess has not been performed on all the depths included in the depthcandidate group (step S205: NO), the decision unit 803 a repeatedlyexecutes the processing at steps S203 and S204 until the contrastcomputation process has been performed on all the depths included in thedepth candidate group.

In contrast, if the contrast computation process has been performed onall the depths included in the depth candidate group (step S205: YES),the decision unit 803 a creates a new depth candidate group includingthe depth with the highest contrast in the latest depth candidate group.Selection of depth candidates for creating a new depth candidate groupis made in the above-described manner. That is, the decision unit 803 acreates a new depth candidate group that includes the depth with thehighest contrast and T depths that have been selected. Subsequently, thedecision unit 803 a performs processing from step S203 to S205 on eachdepth included in the new depth candidate group created (step S206).Subsequently, the decision unit 803 a determines whether the processingat step S206 has been performed a predetermined number of times or not(step S207). If the processing at step S206 has not been performed thepredetermined number of times (step S207: NO), the decision unit 803 arepeatedly executes the processing at step S206 until the predeterminednumber of times is reached.

In contrast, if the processing at step S206 has been performed thepredetermined number of times (step S207: YES), the decision unit 803 adecides the depth with the highest contrast in the final depth candidategroup as the optimal depth for each input image of the camera pair (stepS208). Here, the final depth candidate group represents a depthcandidate group after the processing at step S206 has been performed thepredetermined number of times.

The image processing device 80 a configured as described above canprovide a similar configuration to the eleventh embodiment.

Also, the image processing device 80 a decides optimal depths throughestimation based on a smaller number of depths than in the eleventhembodiment. Thus, it enables faster processing than the eleventhembodiment.

Modification of the Twelfth Embodiment

The twelfth embodiment may be modified similarly to the eleventhembodiment.

A coarse-to-fine method or simplex method may be employed as a processto create a new depth candidate group upon each iteration of processingand decide an optimal solution from the new candidate group created (anoptimal depth in this embodiment).

While this embodiment showed an example where the processing at stepS208 is executed after the processing at step S206 is performed apredetermined number of times, the processing at step S208 may insteadbe performed when a minimum unit of stored depth candidates has beenreached.

While this embodiment showed a configuration that creates a depthcandidate group by selecting from depths registered in the synthesisinformation table, the decision unit 803 a may instead be configured tocreate a depth candidate group so as to include depths other than thedepths registered in the synthesis information table. For example, ifdepth α at a distance of 1 from the virtual viewpoint 82 (depth α=1) anddepth β at a distance of 3 from the virtual viewpoint 82 (depth β=3) areregistered in the synthesis information table, the decision unit 803 acreates a depth candidate group so as to include depth γ at a distanceof 2 from the virtual viewpoint 82 (a depth between depth α and depth β,γ=2), namely a depth between the two depths. In this manner, when depthsother than the depths registered in the synthesis information table areincluded in the depth candidate group and used, the decision unit 803 adetermines conversion information for a depth other than the depthsregistered in the synthesis information table such as by interpolationfrom conversion information for a registered depth. For example,assuming that conversion information is an affine transformation matrixand the affine transformation matrix when depth α=1 is A1_(j1), and theaffine transformation matrix when depth β=3 is A1_(j2), then theelements of the affine transformation matrix for depth γ between depth αand depth β may be determined by averaging the elements of the A1_(j1)matrix and the elements of the A1_(j2) matrix, for example. This exampleis only illustrative; the decision unit 803 a may also create a depthcandidate group so as to include more than one depth as depths betweentwo depths (for example, between depth α and depth β).

The decision unit 803 a may also create a new depth candidate group inthe following manner. The foregoing example of five depths (N=5; fivedepths S1, S2, S3, S4, S5) will be discussed as an example.

(First Method)

A first method is to select a predetermined number of depths between thedepth with the highest contrast and each of the depths neighboring thedepth with the highest contrast, and create a new depth candidate groupincluding the respective sets of predetermined number of selected depthsand the depth with the highest contrast. This will be describedspecifically below.

The decision unit 803 a first defines a “range centered at the depthwith the highest contrast” as described above. That is, if the depthwith the highest contrast is S3, the neighboring depths are S2 and S4,and the range between S2 and S4 is the “range centered at the depth withthe highest contrast”. Here, the range between the depth with thehighest contrast (for example, S3) and one (for example, S2) of thedepths neighboring the depth with the highest contrast is defined as afirst range, and the range between the depth with the highest contrastand the other (for example, S4) of the depths neighboring the depth withthe highest contrast is defined as a second range. The decision unit 803a then selects U (U is an integer equal to or greater than 1) depths inthe first range, and selects V (V is an integer equal to or greaterthan 1) depths in the second range. For example, U depths may beselected at equal intervals from the depths in the first range stored inthe synthesis information table. Likewise, V depths may be selected atequal intervals from the depths in the second range stored in thesynthesis information table, for example. U and V may be the same valueor different values. Subsequently, the decision unit 803 a creates a newdepth candidate group including the depth with the highest contrast (forexample, S3), the U depths selected from the depths in the first range,and the V depths selected from the depths in the second range. That is,the decision unit 803 a creates a new depth candidate group includingU+V+1 depths.

(Second Method)

A second method is to select a predetermined number of depths betweenthe depth with the highest contrast and one of the depths neighboringthe depth with the highest contrast, and create a new depth candidategroup including the predetermined number of selected depths and thedepth with the highest contrast. This will be described specificallybelow.

The decision unit 803 a first defines a “range centered at the depthwith the highest contrast” as described above. That is, if the depthwith the highest contrast is S3, the neighboring depths are S2 and S4,and the range between S2 and S4 is the “range centered at the depth withthe highest contrast”. Here, the range between the depth with thehighest contrast (for example, S3) and one (for example, S2) of thedepths neighboring the depth with the highest contrast is defined as athird range. The decision unit 803 a then selects Z (Z is an integerequal to or greater than 1) depths in the third range. For example, Zdepths may be selected at equal intervals from the depths in the thirdrange stored in the synthesis information table. Subsequently, thedecision unit 803 a creates a new depth candidate group including thedepth with the highest contrast (for example, S3) and the Z depthsselected from the depths in the third range. That is, the decision unit803 a creates a new depth candidate group including Z+1 depths.

Thirteenth Embodiment

The eleventh and twelfth embodiments described configurations thatdecide the optimal depth for each input image of each camera 93 at eachtime. When a synthetic image generated based on optimal depths thusdecided (a virtual omnidirectional image) is reproduced as a video, thevideo can have sense of inconsistency because the optimal depth at eachtime is different. Thus, in the thirteenth embodiment, the imageprocessing device performs a smoothing process so that the optimal depthfor each input image of each camera 93 at each time smoothly changes intime direction. The thirteenth embodiment is described for the casewhere multiple camera pairs are present in the image processing system800 as an example.

FIG. 56 is a schematic block diagram showing a functional configurationof the image processing device 80 b in the thirteenth embodiment. Theimage processing device 80 b has a CPU, memory, and an auxiliary storagedevice connected by a bus, and executes an image processing program. Byexecuting the image processing program, the image processing device 80 bfunctions as a device including the input image storage 801, thesynthesis information storage 802, the decision unit 803 b, the optimaldepth storage 804, the background image storage 805, and the imagesynthesis unit 806. All or some of the functions of the image processingdevice 80 b may be implemented with hardware, such as an ASIC, a PLD, ora FPGA. The image processing program may be recorded in acomputer-readable recording medium. A computer-readable recording mediumis a storage device such as a portable medium like a flexible disk,magneto-optical disk, ROM, or CD-ROM, or a hard disk built in a computersystem, for example. The image processing program may also betransmitted and received via a telecommunication line.

The image processing device 80 b differs from the image processingdevice 80 in configuration in that it includes a decision unit 803 binstead of the decision unit 803. For the remaining configuration, theimage processing device 80 b is similar to the image processing device80. Thus, description on the image processing device 80 b as a whole isomitted and only the decision unit 803 b is described.

The decision unit 803 b takes input images of a camera pair stored inthe input image storage 801 and the synthesis information table storedin the synthesis information storage 802 as input. The decision unit 803b decides the optimal depth for each input image of each camera 93 byperforming similar processing to that by the decision unit 803 of theeleventh embodiment based on the input images of the camera pair and thesynthesis information table input to it. The decision unit 803 b storesthe decided optimal depth in the optimal depth storage 804 as aprovisional optimal depth. The decision unit 803 b takes the provisionaloptimal depth stored in the optimal depth storage 804 as input. Thedecision unit 803 b decides the optimal depth for each input image ofeach camera 93 at each time by smoothing the provisional optimal depthfor each camera 93 in time direction based on the input provisionaloptimal depth. Specific processing by the decision unit 803 b will bedescribed with FIG. 57.

FIG. 57 is a diagram for describing the specific processing by thedecision unit 803 b.

In FIG. 57, the vertical axis represents depth and the horizontal axisrepresents time. The multiple circles shown in FIG. 57 represent theprovisional optimal depths at the individual times. FIG. 57 shows anexample of provisional optimal depth at each time for a certain camera93. Since the provisional optimal depth is decided at each time, therecan be a provisional optimal depth that significantly deviates fromprovisional optimal depths around it, like a circle 992 shown in FIG.57. In such a case, the resulting video can have sense of inconsistencywhen reproduced as a video. Accordingly, the decision unit 803 barranges the value of the provisional optimal depth at each time on thetime axis and smoothes the values so as to be gradual. For example, thedecision unit 803 b determines an estimated value of an optimal depthfrom the provisional optimal depth at each time by polynomialapproximation such that sense of inconsistency is reduced inreproduction as a video. A line 993 shown in FIG. 57 indicates theestimated value of the optimal depth at each time obtained by polynomialapproximation. The decision unit 803 b decides the estimated value ofthe optimal depth at each time obtained by this processing as theoptimal depth for a certain camera 93 at each time. The decision unit803 b then updates the optimal depth by overwriting the provisionaloptimal depth stored in the optimal depth storage 804 with the decidedoptimal depth.

FIG. 58 is a flowchart showing a flow of processing by the imageprocessing device 80 b.

The decision unit 803 b reads input images of a certain camera pair at acertain time from the input image storage 801 (step S301). The decisionunit 803 b then performs a camera pair depth decision process based onthe input image it read out and the synthesis information table storedin the synthesis information storage 802 (step S302). The decision unit803 b determines whether the optimal depths for the input images of allthe camera pairs have been decided or not (step S303). If the optimaldepths for the input images of all the camera pairs have not beendecided (step S303: NO), the decision unit 803 b selects another camerapair (step S304). Here, another camera pair to be selected is a camerapair on which the camera pair depth decision process is not performedyet. Subsequently, the decision unit 803 b performs processing from stepS301 to step S302 on the other camera pair selected.

In contrast, if the optimal depths for the input images of all thecamera pairs have been decided (step S303: YES), the decision unit 803 bdecides the optimal depth for each input image of each camera 93 basedon the decided optimal depth for each input image of the camera pair(step S305). Subsequently, the decision unit 803 b stores the optimaldepth for each input image of each camera 93 decided in the processingat step S305 in the optimal depth storage 804 as a provisional optimaldepth (step S306). The decision unit 803 b determines whether theprocessing from step S301 to step S306 has been performed as often aspredetermined times or not (step S307). If the processing from step S301to step S306 has not been performed as often as the predetermined times(step S307: NO), the decision unit 803 b repeatedly executes theprocessing at step S301 onward.

In contrast, if the processing from step S301 to step S306 has beenperformed as often as the predetermined times (step S307: YES), thedecision unit 803 b performs smoothing in the time direction forprovisional optimal depths corresponding to the predetermined times fora certain camera 93 stored in the optimal depth storage 804 (step S308).For example, the decision unit 803 b determines an estimated value ofthe optimal depth for a certain camera 93 by polynomial approximationfrom the provisional optimal depths corresponding to the predeterminedtimes. Subsequently, the decision unit 803 b stores the estimated valueof the optimal depth for the certain camera 93 as the optimal depth forthe certain camera 93 at each time in the optimal depth storage 804(step S309). The decision unit 803 b determines whether the processingat step S308 and step S309 has been performed on all the cameras 93 ornot (step S310). If the processing at step S308 and step S309 has notbeen performed on all the cameras 93 (step S310: NO), the decision unit803 b repeatedly executes the processing at step S308 and step S309until it has been performed on all the cameras.

In contrast, the processing at step S308 and step S309 has beenperformed on all the cameras 93 (step S310: YES), the image synthesisunit 806 executes an image synthesis process step (step S311).

The image processing device 80 b configured as described above canreduce sense of inconsistency that can occur when virtualomnidirectional images respectively generated using input images at eachtime are output as video. This effect will be described in detail below.

The image processing device 80 b performs smoothing using information onthe provisional optimal depth at each time so that the optimal depthvalues at the individual times are gradual. Thus, even if the optimaldepth at a certain time significantly deviates from other optimaldepths, the image processing device 80 b can correct the optimal depthat the significantly deviating time from optimal depths at times aroundit. Accordingly, it is possible to reduce sense of inconsistency thatcan occur when virtual omnidirectional images respectively generatedusing input images at each time are output as a video.

Modification of the Thirteenth Embodiment

The input image storage 801, the synthesis information storage 802, thedecision unit 803 b, and the optimal depth storage 804 of the imageprocessing device 80 b may be configured as an optimal depth decisionapparatus.

While this embodiment showed a configuration that decides the optimaldepth for each input image of each camera 93 by the decision unit 803 bperforming similar processing to that by the decision unit 803, thedecision unit 803 b may also be configured to decide the optimal depthfor each input image of each camera 93 by performing similar processingto that by the decision unit 803 a.

Fourteenth Embodiment

The fourteenth embodiment describes a case of outputting a virtualomnidirectional image as video in real time. Specifically, thefourteenth embodiment decides the optimal depth for the input image ofcamera 93 at a certain time t based on the optimal depth at a precedingtime (for example, time t−1, t−2). The fourteenth embodiment is alsodescribed for the case where multiple camera pairs are present in theimage processing system 800 as an example.

FIG. 59 is a schematic block diagram representing a functionalconfiguration of an image processing device 80 c in the fourteenthembodiment. The image processing device 80 c has a CPU, memory, and anauxiliary storage device connected by a bus, and executes an imageprocessing program. By executing the image processing program, the imageprocessing device 80 c functions as a device including the input imagestorage 801, the synthesis information storage 802, the decision unit803 c, the optimal depth storage 804 c, the background image storage805, and the image synthesis unit 806. All or some of the functions ofthe image processing device 80 c may be implemented with hardware, suchas an ASIC, a PLD, or a FPGA. The image processing program may berecorded in a computer-readable recording medium. A computer-readablerecording medium is a storage device such as a portable medium like aflexible disk, magneto-optical disk, ROM, or CD-ROM, or a hard diskbuilt in a computer system, for example. The image processing programmay also be transmitted and received via a telecommunication line.

The image processing device 80 c differs from the image processingdevice 80 in configuration in that it includes a decision unit 803 c andan optimal depth storage 804 c instead of the decision unit 803 and theoptimal depth storage 804. For the remaining configuration, the imageprocessing device 80 c is similar to the image processing device 80.Thus, description on the image processing device 80 c as a whole isomitted and only the decision unit 803 c and the optimal depth storage804 c are described.

The optimal depth storage 804 c is configured with a storage device suchas a magnetic hard disk device or a semiconductor storage device. Theoptimal depth storage 804 c stores an optimal depth information table.In the optimal depth information table stored by the optimal depthstorage 804 in the eleventh to thirteenth embodiments, optimal depthinformation for each input image of each camera 93 at each time isregistered. In contrast, in the optimal depth information table storedby the optimal depth storage 804 c in the fourteenth embodiment, optimaldepth information for each input image of each camera 93 at the presenttime (for example, a time when a virtual omnidirectional image forreal-time output is generated) t is not registered (stored) at the startof processing, but optimal depth information for each input image ofeach camera 93 at a time earlier than the present time t (for example,time t−1, t−2, and the like) is registered (stored).

The decision unit 803 c takes the input images of a camera pair storedin the input image storage 801 and the synthesis information tablestored in the synthesis information storage 802 as input. The decisionunit 803 b decides the optimal depth for each input image of each camera93 by performing similar processing to that by the decision unit 803 ofthe eleventh embodiment based on the input images of the camera pair andthe synthesis information table input to it. The decision unit 803 calso decides the optimal depth at the present time t based on optimaldepth information at a time earlier than the present time t (forexample, time t−1, t−2, and the like). As a method for decision based onoptimal depth information at a time earlier than the present time t, thefourteenth embodiment describes an implementation method with a particlefilter, a kind of time series filter. Assume that the number ofparticles to be created in the following processing is P.

FIG. 60 is a flowchart showing a flow of processing by the imageprocessing device 80 c.

The decision unit 803 c reads input images of the camera pair that werecaptured at time t from the input image storage 801 (step S401). At thestart of processing, time t is an initial time. Although the initialtime is typically set to the first time among all times, the idea oftime-series filtering introduced herein can converge to an undesirablevalue as a result of error accumulation (which is called drift). In sucha case, time t+1 may be set as the initial time when an appropriatecondition is satisfied, for example, when maximum likelihood has becomeequal to or smaller than a threshold at time t.

For the input image which has been read out, the decision unit 803 cselects P depth candidates from all depths (for example, depth 1 todepth N) (step S402). A method for selecting P depths from all depths atthe initial time may be randomly selecting P depths, or dividing all thedepths equally into P groups and selecting P depths. At times other thanthe initial time, basically the depth candidate group selected at thepreceding time may be used. The decision unit 803 c computes a predictedvalue of depth using a prediction model for a depth in the depthcandidate group (step S403). Prediction models include uniform linearmotion, uniform acceleration motion, and random walk (this is a stepequivalent to the “prediction” of a common particle filter).

Subsequently, the decision unit 803 c computes a likelihood for thepredicted value of depth computed in the processing at step S303 (stepS404). A method for determining a likelihood may be a contrast withrespect to an overlapping region of a depth decision synthetic imagegenerated based on synthesis information corresponding to a certaindepth. In this case, it is assumed that the higher the contrast, thegreater the likelihood will be (this is a step equivalent to “weighting”of a common particle filter). The decision unit 803 c determines whetherlikelihood has been computed for all depth candidates or not (stepS405). If likelihood has not been computed for all depth candidates ornot (step S405: NO), the decision unit 803 c repeatedly executes theprocessing at steps S402 to S404 until likelihood has been computed forall depth candidates.

In contrast, if likelihood has been computed for all depth candidates(step S405: YES), the decision unit 803 c decides the optimal depth foreach input image of the camera pair at time t based on the likelihoodcomputed in the processing at step S404 (step S406). Methods fordetermining an optimal depth include one that determines the depth withthe highest likelihood as the optimal depth, or one that sets a weightedaverage of likelihoods as the optimal depth (this is a step equivalentto the “state estimation” of a common particle filter). The decisionunit 803 c then selects a depth candidate group at time t+1 based on thelikelihood computed in the processing at step S404 (step S407). A methodfor selecting a depth candidate group at time t+1 based on likelihood isone that employs the magnitude of likelihood. Specifically, for eachdepth, the number of candidates to be selected around that depth isvaried based on the magnitude of likelihood. For example, few candidatesare selected near a depth with low likelihood, while a large number ofcandidates are selected near a depth with high likelihood. The selectionis made so that the total number of candidates is P (this is a stepequivalent to the “resampling” of a common particle filter).

The decision unit 803 c determines whether the processing at step S401to step 407 has been performed on all the camera pairs or not (stepS408). If the processing at step S401 to step 407 has not been performedon all the camera pairs (step S408: NO), the decision unit 803 cperforms processing at step 401 onward on all the camera pairs.

In contrast, if the processing at step S401 to step 407 has beenperformed on all the camera pairs (step S408: YES), the decision unit803 c decides the optimal depth for each input image of each camera 93from the optimal depth for each input image of the camera pair at time t(step S409). Subsequently, the decision unit 803 c stores the optimaldepth for each input image of each camera 93 at time tin the optimaldepth storage 804 c. Subsequently, the image synthesis unit 806 executesthe image synthesis process step (step S410).

The image processing device 80 c configured as described above candecide the optimal depth for an input image of each camera 93 in realtime. This effect will be described in detail below.

The image processing device 80 c estimates an optimal depth for theinput image of each camera 93 at time t from the optimal depth for theinput image at a past time (for example, the immediately precedingtime). Specifically, the image processing device 80 c first computes apredicted value of depth using a prediction model for a depth includedin the depth candidate group for deciding the depth for each input imageof the camera pair at time t. The image processing device 80 c thencomputes the likelihood of the computed predicted value of depth. Then,the image processing device 80 c decides the optimal depth for the inputimages of the camera pair at time t based on the computed likelihood.Subsequently, the image processing device 80 c performs similarprocessing on the input images of all the camera pairs. Accordingly, theoptimal depth for an input image of each camera 93 can be decided inreal time.

Modification of the Fourteenth Embodiment

The input image storage 801, the synthesis information storage 802, thedecision unit 803 c, and the optimal depth storage 804 c of the imageprocessing device 80 c may be configured as an optimal depth decisionapparatus.

In the following, modifications common to the eleventh to fourteenthembodiments are described.

These embodiments are applicable to generation of a synthetic image byoverlaying of images captured by multiple cameras 93 on a backgroundimage, in addition to an omnidirectional image.

Although in these embodiments the values of width registered in thesynthesis information table are the same for all camera IDs, the valueof width may be different from one camera ID to another or different forsome camera IDs.

The decision unit 803 may also decide the optimal depth for eachpredetermined region of one input image.

The eleventh to fourteenth embodiments make it possible to decide theoptimal depth for an image captured by each of multiple image capturingdevices.

While the embodiments of the present invention have been described,specific configurations are not limited to these embodiments, but designmodifications and the like within a range not departing from the spiritof the invention are encompassed in the scope of the invention, ofcourse. The various processes described in the embodiments may beexecuted in parallel or separately depending on the processing abilityof an apparatus executing the process or on any necessity, rather thanbeing executed in time series in accordance with the described order.

[Program and Recording Medium]

When various types of processing functions in the devices described inthe above embodiment are implemented on a computer, the contents ofprocessing function to be contained in each device is written by aprogram. With this program executed on the computer, various types ofprocessing functions in the above-described devices are implemented onthe computer.

This program in which the contents of processing are written can berecorded in a computer-readable recording medium. The computer-readablerecording medium may be any medium such as a magnetic recording device,an optical disc, a magneto-optical recording medium, and a semiconductormemory.

Distribution of this program is implemented by sales, transfer, rental,and other transactions of a portable recording medium such as a DVD anda CD-ROM on which the program is recorded, for example. Furthermore,this program may be stored in a storage of a server computer andtransferred from the server computer to other computers via a network soas to be distributed.

A computer which executes such program first stores the program recordedin a portable recording medium or transferred from a server computeronce in a storage device thereof, for example. When the processing isperformed, the computer reads out the program stored in the recordingmedium thereof and performs processing in accordance with the programthus read out. As another execution form of this program, the computermay directly read out the program from a portable recording medium andperform processing in accordance with the program. Furthermore, eachtime the program is transferred to the computer from the servercomputer, the computer may sequentially perform processing in accordancewith the received program. Alternatively, a configuration may be adoptedin which the transfer of a program to the computer from the servercomputer is not performed and the above-described processing is executedby so-called application service provider (ASP)-type service by whichthe processing functions are implemented only by an instruction forexecution thereof and result acquisition. It should be noted that aprogram according to the present embodiment includes information whichis provided for processing performed by electronic calculation equipmentand which is equivalent to a program (such as data which is not a directinstruction to the computer but has a property specifying the processingperformed by the computer).

In the present embodiment, the present device is configured with apredetermined program executed on a computer. However, the presentdevice may be configured with at least part of these processing contentsrealized in a hardware manner.

What is claimed is:
 1. A virtual reality system that includes a virtualenvironment construction apparatus that constructs a virtual environmentto be used for generating a video based on a real environment in whichanother party launches a flying object, the virtual reality systemcomprising: the virtual environment construction apparatus whichincludes circuitry configured to: generate a presentation sequencerepresenting a time series of scenes to be presented to the user basedon a probability combining a prior probability of a scene of the flyingobject with dynamics representing connection between a plurality ofscenes, decide a presentation trajectory representing a motion of theflying object corresponding to each scene included in the presentationsequence, decide a presentation action representing a motion of theother party corresponding to each scene included in the presentationsequence, and synthesize the virtual environment to be experienced bythe user based on the presentation trajectory and the presentationaction; and a virtual reality head mounted display which presents avideo to the user based on the synthesized virtual environmentconstructed by the virtual environment construction apparatus.
 2. Avirtual reality system that includes a virtual environment constructionapparatus that constructs a virtual environment to be used forgenerating a video based on a real environment in which another partylaunches a flying object, the virtual reality system comprising: thevirtual environment construction apparatus which includes circuitryconfigured to: generate a presentation sequence representing a timeseries of scenes to be presented to the user, decide a presentationtrajectory representing a motion of the flying object corresponding toeach scene included in the presentation sequence, decide a presentationaction representing a motion of the other party different from one inthe real environment corresponding to each scene included in thepresentation sequence, and synthesize the virtual environment to beexperienced by the user based on the presentation trajectory and thepresentation action; and a virtual reality head mounted display whichpresents a video to the user based on the synthesized virtualenvironment constructed by the virtual environment constructionapparatus.
 3. The virtual environment construction apparatus accordingto claim 2, wherein the circuitry is configured to generate thepresentation sequence based on a probability combining a priorprobability of a scene of the flying object with dynamics representingconnection between a plurality of scenes.
 4. The virtual environmentconstruction apparatus according to claim 1 or 3, wherein the circuitryis configured to generate the presentation sequence based on aprobability combining the prior probability of the flying object withthe dynamics for all of a course, a speed, and a pitch type of theflying object, and if none of trajectories of the flying object obtainedfrom the real environment corresponds to the presentation sequence,generates the presentation sequence based on a probability combining theprior probability of the flying object with the dynamics while givingpriority to one of the course, the speed, and the pitch type inaccordance with a practice goal which has been predefined given a sceneto be experienced by the user.
 5. The virtual environment constructionapparatus according to claim 1 or 3, wherein the circuitry is configuredto generate the presentation sequence based on a probability combiningthe prior probability of the flying object with the dynamics for all ofa plurality of parameters relating to flying of the flying object, andif none of trajectories of the flying object obtained from the realenvironment corresponds to the presentation sequence, generates thepresentation sequence based on a probability combining the priorprobability of the flying object with the dynamics while giving priorityto some of the plurality of parameters in accordance with a practicegoal which has been predefined given a scene to be experienced by theuser.
 6. A virtual environment construction method for constructing avirtual environment to be used for generating a video based on a realenvironment in which another party launches a flying object, the virtualenvironment construction method comprising: generating, by circuitry ofa virtual environment construction apparatus, a presentation sequencerepresenting a time series of scenes to be presented to the user basedon a probability combining a prior probability of a scene of the flyingobject with dynamics representing connection between a plurality ofscenes by circuitry of a virtual environment construction apparatus;deciding, by the circuitry, a presentation trajectory representing amotion of the flying object corresponding to each scene included in thepresentation sequence by the circuitry of the virtual environmentconstruction apparatus; deciding, by the circuitry, a presentationaction representing a motion of the other party corresponding to eachscene included in the presentation sequence by the circuitry of thevirtual environment construction apparatus; synthesizing, by thecircuitry, the virtual environment to be experienced by the user basedon the presentation trajectory and the presentation action by thecircuitry of the virtual environment construction apparatus; andpresenting, by a virtual reality head mounted display, a video to theuser based on the synthesized virtual environment.
 7. A virtualenvironment construction method for constructing a virtual environmentto be used for generating a video based on a real environment in whichanother party launches a flying object, the virtual environmentconstruction method comprising: generating, by circuitry of a virtualenvironment construction apparatus, a presentation sequence representinga time series of scenes to be presented to the user by circuitry of avirtual environment construction apparatus; deciding, by the circuitry,a presentation trajectory representing a motion of the flying objectcorresponding to each scene included in the presentation sequence by thecircuitry of the virtual environment construction apparatus; deciding,by the circuitry, a presentation action representing a motion of theother party different from one in the real environment corresponding toeach scene included in the presentation sequence by the circuitry of thevirtual environment construction apparatus; synthesizing, by thecircuitry, the virtual environment to be experienced by the user basedon the presentation trajectory and the presentation action by thecircuitry of the virtual environment construction apparatus; andpresenting, by a virtual reality head mounted display, a video to theuser based on the synthesized virtual environment.
 8. A non-transitorycomputer readable medium including computer executable instructions thatmake a virtual reality system that includes a virtual environmentconstruction apparatus perform a method for a virtual environment to beused for generating a video based on a real environment in which anotherparty launches a flying object, the method comprising: generating, bycircuitry of the virtual environment construction apparatus, apresentation sequence representing a time series of scenes to bepresented to the user based on a probability combining a priorprobability of a scene of the flying object with dynamics representingconnection between a plurality of scenes; deciding, by the circuitry, apresentation trajectory representing a motion of the flying objectcorresponding to each scene included in the presentation sequence;deciding, by the circuitry, a presentation action representing a motionof the other party corresponding to each scene included in thepresentation sequence; synthesizing, by the circuitry, the virtualenvironment to be experienced by the user based on the presentationtrajectory and the presentation action; and presenting, by a virtualreality head mounted display, a video to the user based on thesynthesized virtual environment.
 9. A non-transitory computer readablemedium including computer executable instructions that make a virtualreality system that includes a virtual environment constructionapparatus perform a method for constructing a virtual environment to beused for generating a video based on a real environment in which anotherparty launches a flying object, the method comprising: generating, bycircuitry of the virtual environment construction apparatus, apresentation sequence representing a time series of scenes to bepresented to the user; deciding, by the circuitry, a presentationtrajectory representing a motion of the flying object corresponding toeach scene included in the presentation sequence; deciding, by thecircuitry, a presentation action representing a motion of the otherparty different from one in the real environment corresponding to eachscene included in the presentation sequence; synthesizing, by thecircuitry, the virtual environment to be experienced by the user basedon the presentation trajectory and the presentation action; andpresenting, by a virtual reality head mounted display, a video to theuser based on the synthesized virtual environment.